neoturk - ...Making an active web-page, part 3 using cookies ?...
We've all heard about cookies. In this chapter I will give an example of how to set a cookie, and how to read one. Using cookies is one way to overcome HTTP's stateless nature, and this property is what we are going to make use of in this login-session example. I'm not going to go into details about cookies, but if you want to, check out: www.cookiecentral.com or www.netscape.com
Well let's start. We are going to use a WebModule with three different actions. The actions will be:
Show login page if user is not logged on, else tell user that he has already access. Default action.
If login was OK then send a cookie to the client and show success message. If login wasn't OK, tell user.
Read cookie and if cookie is OK, show protected page, else tell user that he's not authorized.
Set the project:s output directory to: <your server>/cgi-bin and save the project as login.cgi.
What is a cookie ?
Cookies are a list of pair values (Name=Value). In this example we're only going to use one pair, but there could be lot's of them. A cookie could for example hold special user-information used by a Webserver to present a page in a way that's convinient for the user. Or as we will see in this example, identify a user.
To send the cookie to the browser we will use the Response.SetCookiefield method:
ADomain will be blank, APath='/cgi-bin', AExpires = -1 (The Cookie will be killed when we close the browser-session), ASecure=false (In real life you should use a safe connection when using a cookie for this purpose, or else the cookie could be sniffed.)
To read the cookie we will use the Request.CookieFields.Values property.
Let's start the coding with action 2, where we send the cookie with CookieField1='Authorized', if we find 'Delphi6' in the request contentfield: 'PW'
Time to test if it's working. Put http://<your servername>/cgi-bin/login.cgi/prot into your webbrowser and you should get this response:
You're not authorized to view this page!
Put http://<your servername>/cgi-bin/login.cgi into the browser. Login with "Delphi6", and you should get this:
You're authorized to access the protected page. Click button to continue...
Clicking the button should bring you to the protected page:
Welcome to the protected page.
You should now be able to reach the protected page as long as you don't exit your browser-session. If you try and exit your browser and start it again, you will find that you have to login again to reach the protected page.
Delphi - .....................................
neoturk - ...Making an active web-page, part 3 using cookies ?...
We've all heard about cookies. In this chapter I will give an example of how to set a cookie, and how to read one. Using cookies is one way to overcome HTTP's stateless nature, and this property is what we are going to make use of in this login-session example. I'm not going to go into details about cookies, but if you want to, check out: www.cookiecentral.com or www.netscape.com
Well let's start. We are going to use a WebModule with three different actions. The actions will be:
Show login page if user is not logged on, else tell user that he has already access. Default action.
If login was OK then send a cookie to the client and show success message. If login wasn't OK, tell user.
Read cookie and if cookie is OK, show protected page, else tell user that he's not authorized.
Set the project:s output directory to: <your server>/cgi-bin and save the project as login.cgi.
What is a cookie ?
Cookies are a list of pair values (Name=Value). In this example we're only going to use one pair, but there could be lot's of them. A cookie could for example hold special user-information used by a Webserver to present a page in a way that's convinient for the user. Or as we will see in this example, identify a user.
To send the cookie to the browser we will use the Response.SetCookiefield method:
ADomain will be blank, APath='/cgi-bin', AExpires = -1 (The Cookie will be killed when we close the browser-session), ASecure=false (In real life you should use a safe connection when using a cookie for this purpose, or else the cookie could be sniffed.)
To read the cookie we will use the Request.CookieFields.Values property.
Let's start the coding with action 2, where we send the cookie with CookieField1='Authorized', if we find 'Delphi6' in the request contentfield: 'PW'
Time to test if it's working. Put http://<your servername>/cgi-bin/login.cgi/prot into your webbrowser and you should get this response:
You're not authorized to view this page!
Put http://<your servername>/cgi-bin/login.cgi into the browser. Login with "Delphi6", and you should get this:
You're authorized to access the protected page. Click button to continue...
Clicking the button should bring you to the protected page:
Welcome to the protected page.
You should now be able to reach the protected page as long as you don't exit your browser-session. If you try and exit your browser and start it again, you will find that you have to login again to reach the protected page.
Delphi - .....................................
neoturk - ...Indy mailer ?...
If you have used Delphifor Internet programming, you have probably already learned what Indy components are. Indy components allow you to write TCP/IP applications very easily. The Indy components set includes both client and server components, so you could quickly write your own HTTP server if the need arises. Indy components, or Internet Direct more precisely, are now shipped along with Delphi6, but these components are open-source and can be downloaded freely from: www.nevrona.com/indy.
To demonstrate how easy and straightforward programming with Indy is, I made this mail-client.
If you have used Delphifor Internet programming, you have probably already learned what Indy components are. Indy components allow you to write TCP/IP applications very easily. The Indy components set includes both client and server components, so you could quickly write your own HTTP server if the need arises. Indy components, or Internet Direct more precisely, are now shipped along with Delphi6, but these components are open-source and can be downloaded freely from: www.nevrona.com/indy.
To demonstrate how easy and straightforward programming with Indy is, I made this mail-client.
This time I will show you how to make a multithreaded Client/Server-application with Indy. The server will simulate a state change: "working / idle" every 10 secs. The client polls the server at a given interval, and presents the server-state. Possible exceptions are trapped. Try connecting with multiple clients.
Indy components are open-source and can be downloaded freely from: www.nevrona.com/indy.
ShowMessage('The server closed the connection !' + #13#10 +
'Try connecting again.');
end;
end;
end;
procedure TForm1.Button1Click(Sender: TObject);
begin
try
IdTCPClient1.Host:= Edit1.Text;
IdTCPClient1.Connect;
ShowMessage('Connected to ' + Edit1.Text);
Timer1.Interval:= StrToInt(Edit2.Text);
Timer1.Enabled:= true;
except
on EIdConnClosedGracefully do
ShowMessage('The server closed the connection !');
on EIdAlreadyConnected do
ShowMessage('Your''e already connected !');
on EIdSocketError do
ShowMessage('Can''t connect to server !');
end;
end;
procedure TForm1.Button2Click(Sender: TObject);
begin
Timer1.Enabled:= false;
IdTCPClient1.Disconnect;
ShowMessage('Disconnected from ' + Edit1.Text);
end;
end.
Delphi - .....................................
neoturk - ...Indy client - server ?...
This time I will show you how to make a multithreaded Client/Server-application with Indy. The server will simulate a state change: "working / idle" every 10 secs. The client polls the server at a given interval, and presents the server-state. Possible exceptions are trapped. Try connecting with multiple clients.
Indy components are open-source and can be downloaded freely from: www.nevrona.com/indy.
ShowMessage('The server closed the connection !' + #13#10 +
'Try connecting again.');
end;
end;
end;
procedure TForm1.Button1Click(Sender: TObject);
begin
try
IdTCPClient1.Host:= Edit1.Text;
IdTCPClient1.Connect;
ShowMessage('Connected to ' + Edit1.Text);
Timer1.Interval:= StrToInt(Edit2.Text);
Timer1.Enabled:= true;
except
on EIdConnClosedGracefully do
ShowMessage('The server closed the connection !');
on EIdAlreadyConnected do
ShowMessage('Your''e already connected !');
on EIdSocketError do
ShowMessage('Can''t connect to server !');
end;
end;
procedure TForm1.Button2Click(Sender: TObject);
begin
Timer1.Enabled:= false;
IdTCPClient1.Disconnect;
ShowMessage('Disconnected from ' + Edit1.Text);
end;
end.
Delphi - .....................................
neoturk - ...Indy client - server 2 ?...
Another Client/Server-application with Indy.
When a client connects, the server will send back an identity number 0-9 to the client, and show a shape which will indicate the clients condition. The client simulates a state change: "working / idle" every 5 secs. When a client disconnects the associated shape will turn invisible, and the ID-No will be free to use with another client connection. If more than ten client tries to connect, the server will send back a message that it's full, which is also presented at the client side.
Indy components are open-source and can be downloaded freely from: www.nevrona.com/indy.
When a client connects, the server will send back an identity number 0-9 to the client, and show a shape which will indicate the clients condition. The client simulates a state change: "working / idle" every 5 secs. When a client disconnects the associated shape will turn invisible, and the ID-No will be free to use with another client connection. If more than ten client tries to connect, the server will send back a message that it's full, which is also presented at the client side.
Indy components are open-source and can be downloaded freely from: www.nevrona.com/indy.
When Delphi5 first shipped, it included a new, visual container class that represents an important advance in rapid application development (RAD) programming. This class, TFrame, provides you with the ability to visually configure a set of one or more components, and then to easily reuse this configuration throughout your application. This capability is so powerful that Delphi5's integrated development environment (IDE) was re-designed, making extensive use of frames. Frames are now available in C++ Builder 5 and later, as well as Kylix.
This paper provides you with a detailed overview of frames. It begins with a general discussion of what frames are and what benefits they provide. It continues with a demonstration of how to create frames, and how to modify the properties of objects that appear on frame instances. Next, you will learn how to create event handlers for frames, and how to override or extend these event handlers in frame instances. This paper concludes by showing you how to add frames to the Component Palette and the Object Repository, and what benefits you gain by doing so.
Overview of Frames
There are two primary benefits of frames. The first is that, under certain circumstances, frames can dramatically reduce the amount of resources that need to be stored in a project. The second, and generally more important benefit, is that frames permit you to visually create objects that can be duplicated from and extended. These happen to be the same two benefits that you enjoy with visual form inheritance (VFI).
VFI permits you to create form objects that can be inherited from easily. The main limit to VFI is that you must use the form in an all-or-nothing fashion. Specifically, when you use VFI you always create an entirely new form. Frames, on the other hand, are more similar to panels in this respect. That is, a single form can contain two or more frames. Importantly, every frame maintains its relationship with theTFrame class that defines it, meaning that subsequent changes to the defining class are automatically inherited by the instances. While you could achieve a similar effect using TPanels, doing so would be a strictly code-based operation. That is, you would have to write the code to define the TPanel descendants manually. Frames, on the other hand, are designed visually, just like forms.
Frames can also be thought of as sharing some similarities with component templates (a group of one or more components that are saved to the component palette by selecting Component | Create Component Template). But the similarities are limited to the fact that both component templates and frames are designed visually (unlike traditional component design, which is an exclusively code-based process). But the differences between component templates and frames are actually very great. As you have already learned, a frame is an instance of a defining class, and as such, is changed when the defining class is changed. By comparison, component templates are aggregates of components. A change to a component template has no effect on objects previously created from that template.
Creating a Frame
The following steps demonstrate how to create a frame.
1. Begin by selecting File | New Application to create a new project.
2. Select File | New Frame to create a new Frame. Place on this frame 3 Labels and DBEdits. Also place a DBNavigator and a DataSource. Set the Captions of the Labels to ID, First Name, Last Name. Set the DataSource property of each DBEdit as well as the DBNavigator to DataSource1. When you are done the frame may look something like that shown in Figure 1.
Figure 1. A simple frame for displaying an ID number, as well as a first and last name.
3. With this frame still selected, set its Name property to NameFrame. More so than other objects, it is particularly important to give a frame a meaningful name. Finally, save the frame by selecting File | Save As to save this frame. In this case save the frame using the filename NAMEFRAM.PAS.
That's all there is to creating a frame. The following section demonstrates how to use this frame.
Using a Frame
A frame is a component. Its typical use, however, differs from other components that appear on the component palette. The following steps demonstrate how to use a frame.
1. Select Form1 of the application that you started in the preceding steps.
2. Add two group boxes to the form, one above the other. Set the Caption of the first groupbox to Customers and the caption of the second to Employees. Your form may look something like that shown in Figure 2.
Figure 2. A form ready for the placement of frames
3. Now add the frames. With the Standard page of the component palette selected, click on the Frame component and drop it within the Customer groupbox. The designer responds by displaying the Select frame to insert dialog box shown in Figure 3.
Figure 3. The Select frame to insert dialog box
4. Select NameFrame. The frame now appears within the Customer groupbox. Repeat this process, this time placing the frame within the Employee groupbox. You may have to select each frame and correct its size, depending on how you placed it originally. When you are done your form may look something like the one you see in Figure 4.
Figure 4. Two instances of the NameFrame appear on this form
5. Continue by placing two Table components onto the form. Set the DatabaseName property of both tables to IBLocal. Set the TableName property of Table1 to CUSTOMER and the TableName property of Table2 to EMPLOYEE. Make both tables active by setting their Active property to True.
6. Now here is where things get interesting. Select the data source in the Customer frame and set its DataSet property to Table1. Normally you cannot directly select objects that appear within a component. But frames are special. You can select any of the objects that appear within a frame and work with their properties. Next, repeat this operation by selecting the data source in the Employee frame and setting its DataSet property to Table2.
7. Finally, hook up all of the DBEdits. Assign the DataField property of the three DBEdits on the Customer frame to CUST_NO, CONTACT_FIRST, and CONTACT_LAST, respectively. For the Employee frame set the DataField properties of these same DBEdits to EMP_NO, FIRST_NAME, and LAST_NAME.
8. Save this project and then run it. The running project will look something like that shown in Figure 5.
Figure 5. The running frame project
Frames and Inheritance
Up to this point there may seem to be only a little benefit to the use of frames. However, it is when you use the same frame in a number of different situations, and then want to change all instances, that the power of frames really becomes obvious. For example, imagine that you decided that you want your NameFrame to be a read-only frame. This can be accomplished easily by simply changing the original frame. Each frame instance immediately inherits all changes.
You can demonstrate this yourself by following these steps:
1. With the project created in the preceding section open, press Shift-F12 and select NameFrame from the displayed list of forms.
2. Set the AutoEdit property of the DataSource to False.
3. Next, select the DBNavigator, expand its VisibleButtons property, and set the nbInsert, nbDelete, nbEdit, nbPost, and nbCancel flags to False.
4. Now look at your main form. Notice that both of the NameFrame descendants have inherited the changes that you made to the frame. Your frame may now look like the one shown in Figure 6.
Figure 6. Updating the NameFrame automatically causes all instances to be updated as well.
Overriding Contained Component Properties
One of the advantages of frames, one shared with VFI, is that you can change the properties and event handlers associated with the objects inside the inherited frame. These changes override the values inherited. Specifically, subsequent changes to the overridden property in the original frame has no affect on the inherited value.
The following steps demonstrate this behavior:
1. Select the label whose caption is ID in the Customer frame. Using the Object Inspector, change its Caption property to Customer No:. Now select the ID label for the Employee frame and change it to Employee ID:.
2. Press Shift-F12 and select the NameFrame. Change the Caption of this ID label to Identifier.
3. Return to the main form. Notice that the Caption properties of the labels have not changed to Identifier. They still use their overridden values.
This effect is accomplished through information stored in the DFM file. Figure 7 displays a relevant part of the DFM file for this project:
Figure 7. A DFM file containing property overrides for a frame instance
Notice that information about all components contained within the frame whose property values have been changed appear in the frame's inline section of the DFM file. This section, however, only lists those values that have been changed. All other properties are assigned their values based either on the values set for the original frame (and which are stored in the frame's DFM file), or are designated as default values in the individual component's class declarations.
Contained Object Event Handlers
Objects contained within a frame may also have event handlers. While events are simply properties of a method pointer type, they are treated differently than other types of properties when it comes to overriding the default behavior defined for the frame.
Let's begin by considering how an event handler is defined for a frame object. Consider the frame shown in Figure 8. (This code is found in the Frame2 project found in the download for this paper). This frame contains two buttons, one labeled Help and the other labeled Done. (Of course, these captions can be overridden in descendant frames). These buttons also have OnClick event handlers, shown in the following code segment:
Figure 8. A frame with components that have event handlers
Just as the event handlers for objects on a form are published methods of that form's class, the event handlers of objects on a frame are published methods of that frame. (The code segment does not actually depict the fact that these methods are published, but they are declared in the default visibility section of the frame's class declaration, and the default visibility is published.)
If you inspect the code associated with the Button2Click event handler, which is associated with the Done button, you will notice that the fact that the event handlers are associated with the frame introduces an interesting artifact. Specifically, Self is the frame, and not the form in which the frame is contained. Consequently, it is not possible to simply invoke the Close method from within this event handler to close the form. When an unqualified method invocation appears in code, the compiler assumes that you want it to apply to Self. Since a TFrame object does not have a Close method, the compiler generates an error if you simply use an unqualified call to Close.
Since the frame in this example is designed to be embedded within a form, the event handler uses the GetParentComponent method of the frame to climb the containership hierarchy within which the frame is nested. Once a TCustomForm instance is found (which will either be a TForm descendant or a custom form based upon TCustomForm), that reference is used to invoke to containing form's Close method.
Overridding Contained Object Event Handlers
If you are familiar with event overriding in VFI you will recall that the IDE embeds a call to inherited from within an overridden event handler on a descendant form. You can then alter the generated code to either add additional behavior prior to, or following the call to inherited, conditionally invoke inherited, or omit the call altogether.
Frame descendants do not use inherited when invoking the event handler for an object embedded on the parent frame. Instead, the ancestor frame's method is called directly. For example, if you place the TwoButtonFrame frame (shown Figure onto a form and then double-click it, Delphi will generate the following code:
In this generated code TwoButtonFrame1 is an instance of the TTwoButtonFrame (the defining frame class). Button2Click, as you saw in the earlier code segment, is the event handler for the Done button on that frame. As a result, what this code does is to invoke the defining classes riginal event handler, passing to it the Sender that was passed to the button on the frame instance.
This means of event handling introduces another interesting feature. Specifically, in these situations, Sender is generally not a member of the Self object. Indeed, Sender is usually a member of the form object, while Self is the frame object.
The following is an overridden event handler for a TwoButtonFrame instance that was placed on a form. Notice that in this case the original behavior is comment out, meaning that the new behavior completely replaces the originally defined behavior for the Done button.
// The following is the original, auto-generated code
// TwoButtonFrame1.Button2Click(Sender);
end;
The Caption of this button was also overridden, so that it displays the text Start. Figure 9 shows the form on which this TwoButtonFrame descendant appears.
Figure 9. This TwoButtonFrame instances overrides both the Caption and the OnClick event handler.
Frames that Save Resources
The form shown in Figure 9 actually contains two frames. We have already discussed the TwoButtonFrame frame. The second frame is the one that shows the company logo. This frame is named LogoFrame.
The LogoFrame appears on more than one form in the FramDemo project. The alternative to using a frame to display the logo is to place an Image object on each form upon which you want the logo to appear. However, the use of a frame for this purpose significantly reduces the amount of resources that must be compiled into the .EXE, and therefore results in a smaller executable.
The reason for this can be seen if you consider this segment of the DFM file for the form shown in the preceding figure:
inline LogoFrame1: TLogoFrame
Left = 6
Top = 6
Width = 211
Height = 182
inherited Image1: TImage
Width = 211
Height = 182
end
end
If a TImage instance had been placed onto the form instead, the DFM file for the form would have had to contain the entire binary representation of the logo. Furthermore, each and every form containing one of these images would have repeated this resource. However, when a frame is used that resource is defined only once, as shown from this segment of the LogoFrame's DFM file:
Note that this segment includes less than 1% of the entire hexadecimal representation of the binary resource.
Simplifying Frame Usage
Within a single, small project it is fairly easy to use the Frame component on the Standard page of the component palette. But for larger projects, or for situations where you want to use the same frame in multiple applications, you need something easier. Fortunately, Delphi permits you to place individual frames onto the Component Palette, permitting these frames to be used easily and repeatedly, without the extra steps required by the Frame component. A frame can also be placed into the Object Repository, permitting it to be copied or inherited from easily. Both of these techniques are described in the following sections.
Adding a Frame to the Component Palette
By placing a particular frame onto the Component Palette, you make its placement as simple as placing almost any other component. By comparison, using the Frame component on the Standard page of the component palette requires four steps, and limits you to placing frames already defined within your project.
To place a particular frame onto the Component Palette, use the following steps:
1. Save your frame to disk. If you want to use this frame in multiple applications it is highly recommended that you save the frame to a directory that will not be deleted when you update Delphi. For example, create a folder named c:Program FilesBorlandDelphiFrames and store your frames there (you will also want to add this directory to your Library search path using the Enviroment Options dialog box).
2. Select the frame and right-click it. Select Add to Palette. Delphi displays the Component Template Information dialog box.
3. Define the name of the frame component in the Component Name field, the page of the Component Palette on which you want the frame to appear in the Palette page field, and, if you have created a custom 24 x 24 pixel, 16-color icon for the frame, use the Change button to select this bitmap file. Click OK when done.
Using a Frame from the Component Palette
To use a frame previously placed on the Component Palette, use the following steps:
1. Select the page of the Component Palette onto which you saved the frame.
2. Select the frame's icon and drop it onto the form on which you want an instance of that frame to appear. Notice that this process required only two steps, while using the Frame component from the Standard page requires four steps.
Adding a Frame to the Object Repository
By adding a frame to the object repository you make it easy to copy it into a new project. Especially important is the ability to use the inheritance offered by the Object Repository to place an inherited frame into a new project, thereby maintaining the relationship between the frame and its ancestor.
To add a frame to the Object Repository use the following steps:
1. Save your frame to disk. You can save this frame to any directory, including the same one to which you save frames that you add to the Component Palette, to Delphi's OBJREPOS directory, or to a shared directory. (Saving the frame to a shared directory is especially nice if you are using a shared object repository. This permits multiple developers to share one or more frames.)
2. Right-click the frame and select Add to Repository. Delphi responds by displaying the Add to Repository dialog box.
3. Fill out the Add to Repository dialog box just as you would for any template you are adding to the Object Repository. Click OK when done.
Using a Frame from the Object Repository
To use a frame from the Object Repository use the following steps:
1. Select File | New.
2. Select the page of the Object Repository to which you saved your frame template.
3. Select the icon for the frame and then click the Inherit radio button on the Object Repository dialog box.
4. Click OK to add an inherited version of the frame to your project.
Note that if you use the Copy radio button instead of the Inherit radio button, the newly adding frame will be a copy of the original frame. This is useful when you want to create a new frame, but do not want to maintain a relationship between the copy and the original.
Component Palette versus Object Repository
Does is make a difference whether you place a frame that you want to reuse on the Component Palette or the Object Repository? The answer is a strong "Yes!". In most cases you will want to place frames that you want to use frequently onto the Component Palette. When you place a frame from the Component Palette you are always placing an instance of the frame class. You can then easily change the properties and event handlers of this instance, as described earlier in this paper. By comparison, placing a frame from the Object Repository creates a new class, not an instance. This new class is either a copy of the original, or a descendant, depending on which radio button you select on the Object Repository dialog box.
If you want to use a frame in a project I personally think that it makes a great deal of sense to always place an instance, rather than define a new class for your frame. For this purpose, saving the frame to the Component Palette is the best approach.
The one situation where you might want to use the Object Repository is when you are specifically creating hierarchies of frames, where each frame descendant introduces additional objects, methods, or event handlers. Here the inheritance offered by the Object Repository makes it easier for you to create each new descendant. However, once you have define the frame descendants that you want to use regularly, I would again suggest that you add these to the Component Palette to simplify their use.
Turning Frames into True Components
Frames, like other classes that descend from TComponent, can be added to a design-time package in order to place the component on the Component palette. This is an interesting thing to do to a frame class, but it is not something that you will always want to do. Once you have placed a frame onto the Component palette, it is no longer treated as a frame by the designer. Instead it is treated like a compound component. The primary difference is that with a frame you can modify the properties of the objects contained in the frame, but with a compound component you cannot.
Because the power of frames lies in your ability to modify the frame at design time, you might be inclined to rule out ever adding a frame to the component palette. But there are times when adding a frame to the component palette makes a lot of sense. Once you have visually designed the frame, adding it to the component palette locks its features, preventing the component user from making changes to the encapsulated components. Also, once a frame has been added to the component palette, you can easily create an ActiveX wrapper for it.
Summary
A frame is a container class that permits you to visually design compound components. In addition, the design understands the relationship between a frame and the components it contains, permit you to override the properties and event handlers of objects that appear in frame instances. By including frames in your application, you can improve object reuse, reduce maintainance overhead, and make more efficient use of Windows resources.
About the Author
Cary Jensen is President of Jensen Data Systems, Inc., a Houston-based training and consulting company. He is an award-winning, best-selling co-author of eighteen books, including Building Kylix Applications (2001, Osborne Media Group), Oracle JDeveloper (1998, Oracle Press), JBuilder Essentials (1998, Osborne/McGraw-Hill), Delphi In Depth (1996, Osborne/McGraw-Hill), and Programming Paradox 5 for Windows (1995, Sybex). Cary is also Contributing Editor of Delphi Informant Magazine, where he writes the column DBNavigator. He is a popular speaker at conferences, workshops, and training seminars throughout North America and Europe. Cary has a Ph.D. in Human Factors Psychology, specializing in human-computer interaction. You can contact Cary at cjensen@JensenDataSystems.com. The Jensen Data Systems, Inc. web site is at www.JensenDataSystems.com.
Cary is available for onsite training in Delphi and Kylix. For information on available courses, please visit www.JensenDataSystems.com.
Delphi - .....................................
neoturk - ...Application design using frames ?...
When Delphi 5 first shipped, it included a new, visual container class that represents an important advance in rapid application development (RAD) programming. This class, TFrame, provides you with the ability to visually configure a set of one or more components, and then to easily reuse this configuration throughout your application. This capability is so powerful that Delphi 5's integrated development environment (IDE) was re-designed, making extensive use of frames. Frames are now available in C++ Builder 5 and later, as well as Kylix.
This paper provides you with a detailed overview of frames. It begins with a general discussion of what frames are and what benefits they provide. It continues with a demonstration of how to create frames, and how to modify the properties of objects that appear on frame instances. Next, you will learn how to create event handlers for frames, and how to override or extend these event handlers in frame instances. This paper concludes by showing you how to add frames to the Component Palette and the Object Repository, and what benefits you gain by doing so.
Overview of Frames
There are two primary benefits of frames. The first is that, under certain circumstances, frames can dramatically reduce the amount of resources that need to be stored in a project. The second, and generally more important benefit, is that frames permit you to visually create objects that can be duplicated from and extended. These happen to be the same two benefits that you enjoy with visual form inheritance (VFI).
VFI permits you to create form objects that can be inherited from easily. The main limit to VFI is that you must use the form in an all-or-nothing fashion. Specifically, when you use VFI you always create an entirely new form. Frames, on the other hand, are more similar to panels in this respect. That is, a single form can contain two or more frames. Importantly, every frame maintains its relationship with theTFrame class that defines it, meaning that subsequent changes to the defining class are automatically inherited by the instances. While you could achieve a similar effect using TPanels, doing so would be a strictly code-based operation. That is, you would have to write the code to define the TPanel descendants manually. Frames, on the other hand, are designed visually, just like forms.
Frames can also be thought of as sharing some similarities with component templates (a group of one or more components that are saved to the component palette by selecting Component | Create Component Template). But the similarities are limited to the fact that both component templates and frames are designed visually (unlike traditional component design, which is an exclusively code-based process). But the differences between component templates and frames are actually very great. As you have already learned, a frame is an instance of a defining class, and as such, is changed when the defining class is changed. By comparison, component templates are aggregates of components. A change to a component template has no effect on objects previously created from that template.
Creating a Frame
The following steps demonstrate how to create a frame.
1. Begin by selecting File | New Application to create a new project.
2. Select File | New Frame to create a new Frame. Place on this frame 3 Labels and DBEdits. Also place a DBNavigator and a DataSource. Set the Captions of the Labels to ID, First Name, Last Name. Set the DataSource property of each DBEdit as well as the DBNavigator to DataSource1. When you are done the frame may look something like that shown in Figure 1.
Figure 1. A simple frame for displaying an ID number, as well as a first and last name.
3. With this frame still selected, set its Name property to NameFrame. More so than other objects, it is particularly important to give a frame a meaningful name. Finally, save the frame by selecting File | Save As to save this frame. In this case save the frame using the filename NAMEFRAM.PAS.
That's all there is to creating a frame. The following section demonstrates how to use this frame.
Using a Frame
A frame is a component. Its typical use, however, differs from other components that appear on the component palette. The following steps demonstrate how to use a frame.
1. Select Form1 of the application that you started in the preceding steps.
2. Add two group boxes to the form, one above the other. Set the Caption of the first groupbox to Customers and the caption of the second to Employees. Your form may look something like that shown in Figure 2.
Figure 2. A form ready for the placement of frames
3. Now add the frames. With the Standard page of the component palette selected, click on the Frame component and drop it within the Customer groupbox. The designer responds by displaying the Select frame to insert dialog box shown in Figure 3.
Figure 3. The Select frame to insert dialog box
4. Select NameFrame. The frame now appears within the Customer groupbox. Repeat this process, this time placing the frame within the Employee groupbox. You may have to select each frame and correct its size, depending on how you placed it originally. When you are done your form may look something like the one you see in Figure 4.
Figure 4. Two instances of the NameFrame appear on this form
5. Continue by placing two Table components onto the form. Set the DatabaseName property of both tables to IBLocal. Set the TableName property of Table1 to CUSTOMER and the TableName property of Table2 to EMPLOYEE. Make both tables active by setting their Active property to True.
6. Now here is where things get interesting. Select the data source in the Customer frame and set its DataSet property to Table1. Normally you cannot directly select objects that appear within a component. But frames are special. You can select any of the objects that appear within a frame and work with their properties. Next, repeat this operation by selecting the data source in the Employee frame and setting its DataSet property to Table2.
7. Finally, hook up all of the DBEdits. Assign the DataField property of the three DBEdits on the Customer frame to CUST_NO, CONTACT_FIRST, and CONTACT_LAST, respectively. For the Employee frame set the DataField properties of these same DBEdits to EMP_NO, FIRST_NAME, and LAST_NAME.
8. Save this project and then run it. The running project will look something like that shown in Figure 5.
Figure 5. The running frame project
Frames and Inheritance
Up to this point there may seem to be only a little benefit to the use of frames. However, it is when you use the same frame in a number of different situations, and then want to change all instances, that the power of frames really becomes obvious. For example, imagine that you decided that you want your NameFrame to be a read-only frame. This can be accomplished easily by simply changing the original frame. Each frame instance immediately inherits all changes.
You can demonstrate this yourself by following these steps:
1. With the project created in the preceding section open, press Shift-F12 and select NameFrame from the displayed list of forms.
2. Set the AutoEdit property of the DataSource to False.
3. Next, select the DBNavigator, expand its VisibleButtons property, and set the nbInsert, nbDelete, nbEdit, nbPost, and nbCancel flags to False.
4. Now look at your main form. Notice that both of the NameFrame descendants have inherited the changes that you made to the frame. Your frame may now look like the one shown in Figure 6.
Figure 6. Updating the NameFrame automatically causes all instances to be updated as well.
Overriding Contained Component Properties
One of the advantages of frames, one shared with VFI, is that you can change the properties and event handlers associated with the objects inside the inherited frame. These changes override the values inherited. Specifically, subsequent changes to the overridden property in the original frame has no affect on the inherited value.
The following steps demonstrate this behavior:
1. Select the label whose caption is ID in the Customer frame. Using the Object Inspector, change its Caption property to Customer No:. Now select the ID label for the Employee frame and change it to Employee ID:.
2. Press Shift-F12 and select the NameFrame. Change the Caption of this ID label to Identifier.
3. Return to the main form. Notice that the Caption properties of the labels have not changed to Identifier. They still use their overridden values.
This effect is accomplished through information stored in the DFM file. Figure 7 displays a relevant part of the DFM file for this project:
Figure 7. A DFM file containing property overrides for a frame instance
Notice that information about all components contained within the frame whose property values have been changed appear in the frame's inline section of the DFM file. This section, however, only lists those values that have been changed. All other properties are assigned their values based either on the values set for the original frame (and which are stored in the frame's DFM file), or are designated as default values in the individual component's class declarations.
Contained Object Event Handlers
Objects contained within a frame may also have event handlers. While events are simply properties of a method pointer type, they are treated differently than other types of properties when it comes to overriding the default behavior defined for the frame.
Let's begin by considering how an event handler is defined for a frame object. Consider the frame shown in Figure 8. (This code is found in the Frame2 project found in the download for this paper). This frame contains two buttons, one labeled Help and the other labeled Done. (Of course, these captions can be overridden in descendant frames). These buttons also have OnClick event handlers, shown in the following code segment:
Figure 8. A frame with components that have event handlers
Just as the event handlers for objects on a form are published methods of that form's class, the event handlers of objects on a frame are published methods of that frame. (The code segment does not actually depict the fact that these methods are published, but they are declared in the default visibility section of the frame's class declaration, and the default visibility is published.)
If you inspect the code associated with the Button2Click event handler, which is associated with the Done button, you will notice that the fact that the event handlers are associated with the frame introduces an interesting artifact. Specifically, Self is the frame, and not the form in which the frame is contained. Consequently, it is not possible to simply invoke the Close method from within this event handler to close the form. When an unqualified method invocation appears in code, the compiler assumes that you want it to apply to Self. Since a TFrame object does not have a Close method, the compiler generates an error if you simply use an unqualified call to Close.
Since the frame in this example is designed to be embedded within a form, the event handler uses the GetParentComponent method of the frame to climb the containership hierarchy within which the frame is nested. Once a TCustomForm instance is found (which will either be a TForm descendant or a custom form based upon TCustomForm), that reference is used to invoke to containing form's Close method.
Overridding Contained Object Event Handlers
If you are familiar with event overriding in VFI you will recall that the IDE embeds a call to inherited from within an overridden event handler on a descendant form. You can then alter the generated code to either add additional behavior prior to, or following the call to inherited, conditionally invoke inherited, or omit the call altogether.
Frame descendants do not use inherited when invoking the event handler for an object embedded on the parent frame. Instead, the ancestor frame's method is called directly. For example, if you place the TwoButtonFrame frame (shown Figure onto a form and then double-click it, Delphi will generate the following code:
In this generated code TwoButtonFrame1 is an instance of the TTwoButtonFrame (the defining frame class). Button2Click, as you saw in the earlier code segment, is the event handler for the Done button on that frame. As a result, what this code does is to invoke the defining classes riginal event handler, passing to it the Sender that was passed to the button on the frame instance.
This means of event handling introduces another interesting feature. Specifically, in these situations, Sender is generally not a member of the Self object. Indeed, Sender is usually a member of the form object, while Self is the frame object.
The following is an overridden event handler for a TwoButtonFrame instance that was placed on a form. Notice that in this case the original behavior is comment out, meaning that the new behavior completely replaces the originally defined behavior for the Done button.
// The following is the original, auto-generated code
// TwoButtonFrame1.Button2Click(Sender);
end;
The Caption of this button was also overridden, so that it displays the text Start. Figure 9 shows the form on which this TwoButtonFrame descendant appears.
Figure 9. This TwoButtonFrame instances overrides both the Caption and the OnClick event handler.
Frames that Save Resources
The form shown in Figure 9 actually contains two frames. We have already discussed the TwoButtonFrame frame. The second frame is the one that shows the company logo. This frame is named LogoFrame.
The LogoFrame appears on more than one form in the FramDemo project. The alternative to using a frame to display the logo is to place an Image object on each form upon which you want the logo to appear. However, the use of a frame for this purpose significantly reduces the amount of resources that must be compiled into the .EXE, and therefore results in a smaller executable.
The reason for this can be seen if you consider this segment of the DFM file for the form shown in the preceding figure:
inline LogoFrame1: TLogoFrame
Left = 6
Top = 6
Width = 211
Height = 182
inherited Image1: TImage
Width = 211
Height = 182
end
end
If a TImage instance had been placed onto the form instead, the DFM file for the form would have had to contain the entire binary representation of the logo. Furthermore, each and every form containing one of these images would have repeated this resource. However, when a frame is used that resource is defined only once, as shown from this segment of the LogoFrame's DFM file:
Note that this segment includes less than 1% of the entire hexadecimal representation of the binary resource.
Simplifying Frame Usage
Within a single, small project it is fairly easy to use the Frame component on the Standard page of the component palette. But for larger projects, or for situations where you want to use the same frame in multiple applications, you need something easier. Fortunately, Delphi permits you to place individual frames onto the Component Palette, permitting these frames to be used easily and repeatedly, without the extra steps required by the Frame component. A frame can also be placed into the Object Repository, permitting it to be copied or inherited from easily. Both of these techniques are described in the following sections.
Adding a Frame to the Component Palette
By placing a particular frame onto the Component Palette, you make its placement as simple as placing almost any other component. By comparison, using the Frame component on the Standard page of the component palette requires four steps, and limits you to placing frames already defined within your project.
To place a particular frame onto the Component Palette, use the following steps:
1. Save your frame to disk. If you want to use this frame in multiple applications it is highly recommended that you save the frame to a directory that will not be deleted when you update Delphi. For example, create a folder named c:Program FilesBorlandDelphiFrames and store your frames there (you will also want to add this directory to your Library search path using the Enviroment Options dialog box).
2. Select the frame and right-click it. Select Add to Palette. Delphi displays the Component Template Information dialog box.
3. Define the name of the frame component in the Component Name field, the page of the Component Palette on which you want the frame to appear in the Palette page field, and, if you have created a custom 24 x 24 pixel, 16-color icon for the frame, use the Change button to select this bitmap file. Click OK when done.
Using a Frame from the Component Palette
To use a frame previously placed on the Component Palette, use the following steps:
1. Select the page of the Component Palette onto which you saved the frame.
2. Select the frame's icon and drop it onto the form on which you want an instance of that frame to appear. Notice that this process required only two steps, while using the Frame component from the Standard page requires four steps.
Adding a Frame to the Object Repository
By adding a frame to the object repository you make it easy to copy it into a new project. Especially important is the ability to use the inheritance offered by the Object Repository to place an inherited frame into a new project, thereby maintaining the relationship between the frame and its ancestor.
To add a frame to the Object Repository use the following steps:
1. Save your frame to disk. You can save this frame to any directory, including the same one to which you save frames that you add to the Component Palette, to Delphi's OBJREPOS directory, or to a shared directory. (Saving the frame to a shared directory is especially nice if you are using a shared object repository. This permits multiple developers to share one or more frames.)
2. Right-click the frame and select Add to Repository. Delphi responds by displaying the Add to Repository dialog box.
3. Fill out the Add to Repository dialog box just as you would for any template you are adding to the Object Repository. Click OK when done.
Using a Frame from the Object Repository
To use a frame from the Object Repository use the following steps:
1. Select File | New.
2. Select the page of the Object Repository to which you saved your frame template.
3. Select the icon for the frame and then click the Inherit radio button on the Object Repository dialog box.
4. Click OK to add an inherited version of the frame to your project.
Note that if you use the Copy radio button instead of the Inherit radio button, the newly adding frame will be a copy of the original frame. This is useful when you want to create a new frame, but do not want to maintain a relationship between the copy and the original.
Component Palette versus Object Repository
Does is make a difference whether you place a frame that you want to reuse on the Component Palette or the Object Repository? The answer is a strong "Yes!". In most cases you will want to place frames that you want to use frequently onto the Component Palette. When you place a frame from the Component Palette you are always placing an instance of the frame class. You can then easily change the properties and event handlers of this instance, as described earlier in this paper. By comparison, placing a frame from the Object Repository creates a new class, not an instance. This new class is either a copy of the original, or a descendant, depending on which radio button you select on the Object Repository dialog box.
If you want to use a frame in a project I personally think that it makes a great deal of sense to always place an instance, rather than define a new class for your frame. For this purpose, saving the frame to the Component Palette is the best approach.
The one situation where you might want to use the Object Repository is when you are specifically creating hierarchies of frames, where each frame descendant introduces additional objects, methods, or event handlers. Here the inheritance offered by the Object Repository makes it easier for you to create each new descendant. However, once you have define the frame descendants that you want to use regularly, I would again suggest that you add these to the Component Palette to simplify their use.
Turning Frames into True Components
Frames, like other classes that descend from TComponent, can be added to a design-time package in order to place the component on the Component palette. This is an interesting thing to do to a frame class, but it is not something that you will always want to do. Once you have placed a frame onto the Component palette, it is no longer treated as a frame by the designer. Instead it is treated like a compound component. The primary difference is that with a frame you can modify the properties of the objects contained in the frame, but with a compound component you cannot.
Because the power of frames lies in your ability to modify the frame at design time, you might be inclined to rule out ever adding a frame to the component palette. But there are times when adding a frame to the component palette makes a lot of sense. Once you have visually designed the frame, adding it to the component palette locks its features, preventing the component user from making changes to the encapsulated components. Also, once a frame has been added to the component palette, you can easily create an ActiveX wrapper for it.
Summary
A frame is a container class that permits you to visually design compound components. In addition, the design understands the relationship between a frame and the components it contains, permit you to override the properties and event handlers of objects that appear in frame instances. By including frames in your application, you can improve object reuse, reduce maintainance overhead, and make more efficient use of Windows resources.
About the Author
Cary Jensen is President of Jensen Data Systems, Inc., a Houston-based training and consulting company. He is an award-winning, best-selling co-author of eighteen books, including Building Kylix Applications (2001, Osborne Media Group), Oracle JDeveloper (1998, Oracle Press), JBuilder Essentials (1998, Osborne/McGraw-Hill), Delphi In Depth (1996, Osborne/McGraw-Hill), and Programming Paradox 5 for Windows (1995, Sybex). Cary is also Contributing Editor of Delphi Informant Magazine, where he writes the column DBNavigator. He is a popular speaker at conferences, workshops, and training seminars throughout North America and Europe. Cary has a Ph.D. in Human Factors Psychology, specializing in human-computer interaction. You can contact Cary at cjensen@JensenDataSystems.com. The Jensen Data Systems, Inc. web site is at www.JensenDataSystems.com.
Cary is available for onsite training in Delphi and Kylix. For information on available courses, please visit www.JensenDataSystems.com.
Delphi - .....................................
neoturk - ...Simple html to text converter ?...
I often get questions like: "How can I cut out the text I wan't from a HTML-file ?"
One way to do this is to first remove all taginformation, and make a clean textfile of it. How can I do that? Well it's quite simple. A HTML-file consists of tags and text. Everything that's surrounded by a '<' and a '>' - character is what we call tags. Tags is information which the webbrowser will respond to in different ways. On the other hand, things between a '>' and '<' is pure text (with some exceptions), which the browser will write to the screen.
Lets consider two exceptions in our simple converter: ' ' - nonbreaking space and '"' - quotation mark.
Let's convert the break-tag '<BR>' to a carriage return (#13#10).
Finally we delete empty lines and save the file with a txt-extension.
I often get questions like: "How can I cut out the text I wan't from a HTML-file ?"
One way to do this is to first remove all taginformation, and make a clean textfile of it. How can I do that? Well it's quite simple. A HTML-file consists of tags and text. Everything that's surrounded by a '<' and a '>' - character is what we call tags. Tags is information which the webbrowser will respond to in different ways. On the other hand, things between a '>' and '<' is pure text (with some exceptions), which the browser will write to the screen.
Lets consider two exceptions in our simple converter: ' ' - nonbreaking space and '"' - quotation mark.
Let's convert the break-tag '<BR>' to a carriage return (#13#10).
Finally we delete empty lines and save the file with a txt-extension.
neoturk - ...Creating asp com objects with delphi 5-6 ?...
Creating ASP com objects, or Active Server Objects with Delphi 5-6 is very easy, once you know how to do it!
What follows is a step by step instruction for creating your first ASP com object.
File - New - ActiveX - ActiveX Library
File - New - ActiveX - Active Server Object
CoClassName=janaspdemo
Instancing=Muliple Instance
Threading Model=Both
Active Server Type=Page Level Events Model
Options= (checked) Generate a template test script for this object
In the type libary editor select Ijanaspdemo
Click Method on the toolbar and enter report as method name.
Select the parameters tab
Click under Name and type strInOut
Click under Type and select Variant*
Click under Modifier, click the ellipsed and check In and Out in the flags popup
Click Refresh on the toolbar
Move the type library editor window away so that you can see Unit1 which was generated by the type library editor.
Press ctrl+F12 (view units) and select Project1_TLB
Have a look at the type library generated by the editor. You normally don't have to touch the Porject1_TLB unit, as the type library editor will do the changes for you.
View Unit1 , positition the cursor on procedure report and press ctrl+shift+down to jump to the procedure report implementation. You can see that the type library editor has created an empty sceleton for you.
For the time being just type // implement later between the begin and end;
Switch back to the type library editor.
In the type libary editor select Ijanaspdemo
Click Property Read/Write on the toolbar
Change the first property1 name to heading. The second porperty1 will be automatically changed to heading as well.
Select the first heading, the one with modifier [out,retval] and long* as Type.
Click under Type and select Variant* (we want the header to be a string, not an integer)
Select the second heading, the one with modifier [in] and long as Type.
Click under Type and select BSTR.
Click Refresh on the toolbar.
Now first have a look in Project1_TLB and look below: Ijanaspdemo = interface(IDispatch)
See how the type library editor has added three lines:
Note that you don't see a property here, just the Get_heading and Set_heading function and procedure.
Note
When adding methods or properties to an Active Server Object, always do this in the type library editor. This will create the code for you, both in Project1_TLB and in Unit1.
Put the cursor on function get_heading and press ctrl+shift+down to jump to the implementation part.
See that it is still empy. In this case I want both the get_heading and the set_heading to use a private field.
Go to the top and insert the private FHeading as shown below:
type
Tjanaspdemo = class(TASPObject, Ijanaspdemo)
private
FHeading:widestring;
protected
procedure OnEndPage; safecall;
You don't have to do this is you want to handle your header in a different way, but many times you just want to use a private field of the object.
Now go the Get_heading implementation and type:
result:=FHeading;
Go to the Set_heading implementation and type:
FHeading:=Value;
Now it is time to save your project.
Press the Save All button on the IDE toolbar.
Save the unit as janspdemoU.pas
Save the asp template as janaspdemo.asp
Save the project as janaspdemo.
Build the project and register the asp component with Run - Register ActiveX Server.
Your janaspdemo component is contained within the just generated janaspdemo.dll.
Modify the asp file
You are now ready to modify the asp template.
Open it with e.g. Notepad.
It contains the following:
<HTML>
<BODY>
<TITLE> Testing Delphi ASP </TITLE>
<CENTER>
<H3> You should see the results of your Delphi Active Server method below </H3>
</CENTER>
<HR>
<% Set DelphiASPObj = Server.CreateObject("janaspdemo.janaspdemo")
DelphiASPObj.{Insert Method name here}
%>
<HR>
</BODY>
</HTML>
Change Server.CreateObject("Project1.janaspdemo") to
Server.CreateObject("janaspdemo.janaspdemo")
Change DelphiASPObj.{Insert Method name here} to
DelphiASPObj.heading ="my first aspdemo heading"
Response.write DelphiASPObj.heading
Save janaspdemo.asp
We are not ready yet but first something important:
When you request an asp page in your browser from Personal Web Server, any dll loaded will remain in memory, even after you move to a different page, or after you closed your browser, or even after you stopped PWS. This means that when in Delphi you try to make changes and recompile you get a message telling you that the output file can not be created. This is because it has not been released from memory.
Can we then only recompile after we have restarted the computer?
How do I unlock a Active Server Library DLL?
At first I thought that the only way to unlock a ASP component DLL was to reboot the computer. There is however a better way.
Create a new start menu shortcut:
c:windowssysteminetsrvpws.exe /stop /y
It is the /y that does the trick. Not only will it stop PWS, as does the stop button in the Personal Web Manager, but it will also unload the Inetinfo.exe process from memory, unlocking any locked ASP component library DLL's.
This way you can compile your ASP component with Delphi, start your web application and use the just created shortcut to unload the DLL from memory, allowing you to recompile from Delphi without rebooting your computer. A big time saver!
C:WINDOWSSYSTEMinetsrvinetinfo.exe -e w3svc will restart PWS
Unlocking Active Server Library DLL's under Windows NT
Type net stop iisadmin /y to shutdown the parent service of IIS, IIS Admin. This will also shut down FTP, STMP, and any other services that are children of IIS Admin. It will unload the inetinfo.exe process from memory. If you type only net stop w3svc, to unload just the Web server, inetinfo.exe will not be unloaded.
Type net start w3svc to restart the Web server.
So how do I test an asp component?
The way to go here is to create a new project specifically for testing your asp component.
Somethings just can't be checked within a test project but most routines can be checked and tested and it will save you a lot of rebooting.
Create a test application
As explained above, asp components created with server.createobject stay in memory until you shutdown your computer. This prohibits recompiling from Delphi. So the way out is a test application.
Start a new Delphi project with File - New Application.
Add a private field to the form: FVar:OleVariant;
In the formcreate event handler include: FVar:=createoleobject('janaspdemo.janaspdemo');
In the formdestroy event handler include: FVar:=Unassigned;
You can now add buttons,menu items, text boxes etc, to the form. Whatever you need to test the asp component.
You can set the heading with: Fvar.heading:="my first heading";
Or retrieve it with s:=Fvar.heading;
Delphi - .....................................
neoturk - ...Creating asp com objects with delphi 5-6 ?...
Creating ASP com objects, or Active Server Objects with Delphi 5-6 is very easy, once you know how to do it!
What follows is a step by step instruction for creating your first ASP com object.
File - New - ActiveX - ActiveX Library
File - New - ActiveX - Active Server Object
CoClassName=janaspdemo
Instancing=Muliple Instance
Threading Model=Both
Active Server Type=Page Level Events Model
Options= (checked) Generate a template test script for this object
In the type libary editor select Ijanaspdemo
Click Method on the toolbar and enter report as method name.
Select the parameters tab
Click under Name and type strInOut
Click under Type and select Variant*
Click under Modifier, click the ellipsed and check In and Out in the flags popup
Click Refresh on the toolbar
Move the type library editor window away so that you can see Unit1 which was generated by the type library editor.
Press ctrl+F12 (view units) and select Project1_TLB
Have a look at the type library generated by the editor. You normally don't have to touch the Porject1_TLB unit, as the type library editor will do the changes for you.
View Unit1 , positition the cursor on procedure report and press ctrl+shift+down to jump to the procedure report implementation. You can see that the type library editor has created an empty sceleton for you.
For the time being just type // implement later between the begin and end;
Switch back to the type library editor.
In the type libary editor select Ijanaspdemo
Click Property Read/Write on the toolbar
Change the first property1 name to heading. The second porperty1 will be automatically changed to heading as well.
Select the first heading, the one with modifier [out,retval] and long* as Type.
Click under Type and select Variant* (we want the header to be a string, not an integer)
Select the second heading, the one with modifier [in] and long as Type.
Click under Type and select BSTR.
Click Refresh on the toolbar.
Now first have a look in Project1_TLB and look below: Ijanaspdemo = interface(IDispatch)
See how the type library editor has added three lines:
Note that you don't see a property here, just the Get_heading and Set_heading function and procedure.
Note
When adding methods or properties to an Active Server Object, always do this in the type library editor. This will create the code for you, both in Project1_TLB and in Unit1.
Put the cursor on function get_heading and press ctrl+shift+down to jump to the implementation part.
See that it is still empy. In this case I want both the get_heading and the set_heading to use a private field.
Go to the top and insert the private FHeading as shown below:
type
Tjanaspdemo = class(TASPObject, Ijanaspdemo)
private
FHeading:widestring;
protected
procedure OnEndPage; safecall;
You don't have to do this is you want to handle your header in a different way, but many times you just want to use a private field of the object.
Now go the Get_heading implementation and type:
result:=FHeading;
Go to the Set_heading implementation and type:
FHeading:=Value;
Now it is time to save your project.
Press the Save All button on the IDE toolbar.
Save the unit as janspdemoU.pas
Save the asp template as janaspdemo.asp
Save the project as janaspdemo.
Build the project and register the asp component with Run - Register ActiveX Server.
Your janaspdemo component is contained within the just generated janaspdemo.dll.
Modify the asp file
You are now ready to modify the asp template.
Open it with e.g. Notepad.
It contains the following:
<HTML>
<BODY>
<TITLE> Testing Delphi ASP </TITLE>
<CENTER>
<H3> You should see the results of your Delphi Active Server method below </H3>
</CENTER>
<HR>
<% Set DelphiASPObj = Server.CreateObject("janaspdemo.janaspdemo")
DelphiASPObj.{Insert Method name here}
%>
<HR>
</BODY>
</HTML>
Change Server.CreateObject("Project1.janaspdemo") to
Server.CreateObject("janaspdemo.janaspdemo")
Change DelphiASPObj.{Insert Method name here} to
DelphiASPObj.heading ="my first aspdemo heading"
Response.write DelphiASPObj.heading
Save janaspdemo.asp
We are not ready yet but first something important:
When you request an asp page in your browser from Personal Web Server, any dll loaded will remain in memory, even after you move to a different page, or after you closed your browser, or even after you stopped PWS. This means that when in Delphi you try to make changes and recompile you get a message telling you that the output file can not be created. This is because it has not been released from memory.
Can we then only recompile after we have restarted the computer?
How do I unlock a Active Server Library DLL?
At first I thought that the only way to unlock a ASP component DLL was to reboot the computer. There is however a better way.
Create a new start menu shortcut:
c:windowssysteminetsrvpws.exe /stop /y
It is the /y that does the trick. Not only will it stop PWS, as does the stop button in the Personal Web Manager, but it will also unload the Inetinfo.exe process from memory, unlocking any locked ASP component library DLL's.
This way you can compile your ASP component with Delphi, start your web application and use the just created shortcut to unload the DLL from memory, allowing you to recompile from Delphi without rebooting your computer. A big time saver!
C:WINDOWSSYSTEMinetsrvinetinfo.exe -e w3svc will restart PWS
Unlocking Active Server Library DLL's under Windows NT
Type net stop iisadmin /y to shutdown the parent service of IIS, IIS Admin. This will also shut down FTP, STMP, and any other services that are children of IIS Admin. It will unload the inetinfo.exe process from memory. If you type only net stop w3svc, to unload just the Web server, inetinfo.exe will not be unloaded.
Type net start w3svc to restart the Web server.
So how do I test an asp component?
The way to go here is to create a new project specifically for testing your asp component.
Somethings just can't be checked within a test project but most routines can be checked and tested and it will save you a lot of rebooting.
Create a test application
As explained above, asp components created with server.createobject stay in memory until you shutdown your computer. This prohibits recompiling from Delphi. So the way out is a test application.
Start a new Delphi project with File - New Application.
Add a private field to the form: FVar:OleVariant;
In the formcreate event handler include: FVar:=createoleobject('janaspdemo.janaspdemo');
In the formdestroy event handler include: FVar:=Unassigned;
You can now add buttons,menu items, text boxes etc, to the form. Whatever you need to test the asp component.
You can set the heading with: Fvar.heading:="my first heading";
Or retrieve it with s:=Fvar.heading;
Delphi - .....................................
neoturk - ...Date-time-day client-server with com ?...
This example shows step by step how to make a COM Client-Server application that informs about current date, time and weekday. The Server will have three methods: GetDate, GetTime and GetWeekDay. The server could run local or remote.
The Server:
Select: New application.
Put a Label on the Form and in the caption write: "DateTimeDay-server" or whatever you like. This form will be shown when the server executes.
Select: New-ActiveX-Automation Object.
Give the Object a CoClass name: MasDateTime
Instancing: Multiple instance
Threading model: Both
Click OK.
In the Project-Library wizard:
Click on the interface: IMasDateTime
Select: New - Method. Give the method a name: GetDate
Select: Parameters - and in return type select: widestring (or BSTR* if you're using IDL. You can change this if you wan't to: Select Tools/Environmental options/Type Library and change Language.)
Do the same with GetTime and GetWeekDay.
Refresh implementation, and save the project as: MasTDD.dpr.
If everything is OK, your project should consist of: Unit1 and Form1, Unit2 and the typelibrary: MasTDD_TLB.
The typelibrary is where the description of your interface is, normally you don't have to change here. Unit2 is where the implementation is done.
Take a look at Unit2. As you can see, the wizard has already made a skeleton for your methods. Let's fill it with some code:
function TMasDateTime.GetDate: WideString;
begin
Result:= DateToStr(Now);
end;
function TMasDateTime.GetTime: WideString;
begin
Result:= TimeToStr(Now);
end;
function TMasDateTime.GetWeekDay: WideString;
var
Day: integer;
begin
Day:= DayOfTheWeek(Now);
case Day of
1: Result:= 'Monday';
2: Result:= 'Tuesday';
3: Result:= 'Wednesday';
4: Result:= 'Thursday';
5: Result:= 'Friday';
6: Result:= 'Saturday';
7: Result:= 'Sunday';
end;
end;
Put: SysUtils, DateUtils in the Uses clause.
Compile and save the project.
The Client :
Choose: New application.
Put five buttons, a Label and an EditBox on the Form.
Save the unit as Cl.pas and the project as Client.dpr
Put: MASTDD_TLB in the upper uses clause:
Put this code in the private clause:
Server: IMasDateTime;
Here's the rest of the code:
implementation
{$R *.dfm}
procedure TForm1.Button1Click(Sender: TObject);
begin
ShowMessage(Server.GetDate);
end;
procedure TForm1.Button4Click(Sender: TObject);
begin
Server:= CoMasDateTime.CreateRemote(Edit1.Text);
end;
procedure TForm1.Button2Click(Sender: TObject);
begin
ShowMessage(Server.GetTime);
end;
procedure TForm1.Button3Click(Sender: TObject);
begin
ShowMessage(Server.GetWeekDay);
end;
procedure TForm1.Button5Click(Sender: TObject);
begin
Server:= CoMasDateTime.Create;
end;
end.
Delphi - .....................................
neoturk - ...Date-time-day client-server with com ?...
This example shows step by step how to make a COM Client-Server application that informs about current date, time and weekday. The Server will have three methods: GetDate, GetTime and GetWeekDay. The server could run local or remote.
The Server:
Select: New application.
Put a Label on the Form and in the caption write: "DateTimeDay-server" or whatever you like. This form will be shown when the server executes.
Select: New-ActiveX-Automation Object.
Give the Object a CoClass name: MasDateTime
Instancing: Multiple instance
Threading model: Both
Click OK.
In the Project-Library wizard:
Click on the interface: IMasDateTime
Select: New - Method. Give the method a name: GetDate
Select: Parameters - and in return type select: widestring (or BSTR* if you're using IDL. You can change this if you wan't to: Select Tools/Environmental options/Type Library and change Language.)
Do the same with GetTime and GetWeekDay.
Refresh implementation, and save the project as: MasTDD.dpr.
If everything is OK, your project should consist of: Unit1 and Form1, Unit2 and the typelibrary: MasTDD_TLB.
The typelibrary is where the description of your interface is, normally you don't have to change here. Unit2 is where the implementation is done.
Take a look at Unit2. As you can see, the wizard has already made a skeleton for your methods. Let's fill it with some code:
function TMasDateTime.GetDate: WideString;
begin
Result:= DateToStr(Now);
end;
function TMasDateTime.GetTime: WideString;
begin
Result:= TimeToStr(Now);
end;
function TMasDateTime.GetWeekDay: WideString;
var
Day: integer;
begin
Day:= DayOfTheWeek(Now);
case Day of
1: Result:= 'Monday';
2: Result:= 'Tuesday';
3: Result:= 'Wednesday';
4: Result:= 'Thursday';
5: Result:= 'Friday';
6: Result:= 'Saturday';
7: Result:= 'Sunday';
end;
end;
Put: SysUtils, DateUtils in the Uses clause.
Compile and save the project.
The Client :
Choose: New application.
Put five buttons, a Label and an EditBox on the Form.
Save the unit as Cl.pas and the project as Client.dpr
Put: MASTDD_TLB in the upper uses clause:
Put this code in the private clause:
Server: IMasDateTime;
Here's the rest of the code:
implementation
{$R *.dfm}
procedure TForm1.Button1Click(Sender: TObject);
begin
ShowMessage(Server.GetDate);
end;
procedure TForm1.Button4Click(Sender: TObject);
begin
Server:= CoMasDateTime.CreateRemote(Edit1.Text);
end;
procedure TForm1.Button2Click(Sender: TObject);
begin
ShowMessage(Server.GetTime);
end;
procedure TForm1.Button3Click(Sender: TObject);
begin
ShowMessage(Server.GetWeekDay);
end;
procedure TForm1.Button5Click(Sender: TObject);
begin
Server:= CoMasDateTime.Create;
end;
end.
Delphi - .....................................
neoturk - ...Email validation ?...
Here is a little function that will validate an EMail-address.
It will check the EMail:s basic construction with five different tests.
You cannot, of course, be sure that the address will be a working one, but at least it will have all chances to it!
Here is what it will check:
That the "@"-character is present.
That there's at least one character before "@".
That there's at least one dot (".") after "@".
That there's at least one character between "@" and the dot.
That there's at least one character after the dot.
function EMailValid(EMail: string): Boolean;
begin
Result:= false;
if Pos('@', EMail) > 0 then
if Length(Copy(EMail, 1, Pos('@', EMail) - 1)) > 0 then
if Pos('.', Copy(EMail, Pos('@', EMail) + 1, 1000)) > 0 then
if Length(Copy(EMail, Pos('@', EMail) + 1, Pos('.', Copy(EMail, Pos('@',
EMail) + 1, 1000)))) > 0 then
if Length(Copy(EMail, Pos('.', EMail) + 1, 1000)) > 0 then
Result:= true;
end;
Delphi - .....................................
neoturk - ...Email validation ?...
Here is a little function that will validate an EMail-address.
It will check the EMail:s basic construction with five different tests.
You cannot, of course, be sure that the address will be a working one, but at least it will have all chances to it!
Here is what it will check:
That the "@"-character is present.
That there's at least one character before "@".
That there's at least one dot (".") after "@".
That there's at least one character between "@" and the dot.
That there's at least one character after the dot.
function EMailValid(EMail: string): Boolean;
begin
Result:= false;
if Pos('@', EMail) > 0 then
if Length(Copy(EMail, 1, Pos('@', EMail) - 1)) > 0 then
if Pos('.', Copy(EMail, Pos('@', EMail) + 1, 1000)) > 0 then
if Length(Copy(EMail, Pos('@', EMail) + 1, Pos('.', Copy(EMail, Pos('@',
EMail) + 1, 1000)))) > 0 then
if Length(Copy(EMail, Pos('.', EMail) + 1, 1000)) > 0 then
Result:= true;
end;
Delphi - .....................................
neoturk - ...Drag - drop example ?...
Have you ever been using WinAmp? If you haven't, I could tell you that it's a widely spread freeware
music-mediaplayer, where you can have a tracklist with your favourite songs. The songs in this list could very
easy be moved to any position with the use of drag & drop functionality.
This example shows how to implement it with Delphi.
onto a form and then double-click it,