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The LA Fox Developer Newsletter
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March 1998
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This article is designed to be ushort and to the point.” It tells you how to subclass the Visual FoxPro bases classes, but not why you want to do that. There are plenty of explanations in books and the trade rags as to why you should subclass the VFP base classes. Trust me
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you don’t want to work directly with the VFP bases classes. Always work with your subclassed version of the VFP base classes and you’ll be a productive, happy programmer with a good bit more hair. That having been said, let’s get straight to the point of this article.
Open a new, non-wizard form by clicking the File menu and selecting New (FiIe:New). Choose Form as the file type and click New File. Ensure that the Form Controls toolbar is visible. The standard toolbar is shown in figure 1.
If you have a form open and you don’t see this toolbar, click View:Toolbars, check Form Controls and click OK. Now that we
can
When you pick controls from the standard Forms Control toolbar, you’re using VFP’s base classes. That is exactly what you don’t want to do! So how do we get controls on forms without using this standard toolbar? Well, you’ve got to create your own toolbar with your own controls. That’s really not hard and we’ll do it right now.
To get started, click FiIe:New, select Class as the file type, then click New File. This will bring up the dialog box pictured in figure 2.
From this dialog box you are about to create a class that is stored in a class library. We’ll create these classes in a specific order so that they appear on your toolbar in the same order as they do on the standard toolbar. Name the class something meaningful to you. I just use the base class name
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with an 'i" at the beginning. The Based On combobox should say Separator. The Store In field is where you’ll put the name of the visual class library in which this class will be stored. Please note that you can click on the button to the right of this field to navigate to a particular drive and folder and even create new folders as you go thanks to the Win95 interface. Put the path and file name in this field and make sure you put it into a “common” directory for development purposes, not a directory that contains a particular project. When you’re done, click OK.
When you’ve clicked OK, the Class Designer will appear with what looks like a teeny, tiny form in it. Leave it be. You have created a single class (a subclass of the FoxPro separator base class) in a Visual class library. Not real hard was it? Later, you’ll add this library as a toolbar into the VFP environment. Now all you have to do is add a subclass for each of the VFP base classes to this same visual class library. That’s not hard
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it’s almost the same as adding the first one, but you just repeat it for each VFP base class.
To do this, simply close the Class Designer. Then click Tools:Class Browser, navigate to the directory where you created your visual class library, and double-click on it to open it in the Class Browser. The Class Browser should look something like figure 3. Note that it has your separator class in it.
From the Class Browser, you will add additional classes based on the VFP base classes until you have your visual class library filled up with subclasses of each of those base classes (actually in this article we’re only dealing with control classes that can be placed on a form). Then you’ll be able to add it as a toolbar to the FoxPro environment and pick controls from itto be placed on a form. At that point, all your controls will be based on subclasses of the base classes and not the base classes themselves. This is the goal we are shooting for. The next section explains about how to go about these final steps.
Your class library now has one class in it
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your subclassed version of the separator base class. Completing the task of subclassing all the base classes is just a matter of adding a
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Figure 1
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Figure 3
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Figure 2
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