Subclassing

Subclassing objects and procedures is a powerful technique you can build into your template to change the way that standard Visual Basic elements work. You could, for example, subclass Visual Basic's Load method. "Why would I want to do this?" you ask. Well, imagine an application with a complex-state engine that must control what forms can be loaded depending on application state (not an uncommon requirement). By subclassing the Load method, you will effectively channel every load request via your function. You can then determine what is being loaded and either prevent the load from occurring, or permit it. In effect, all the state code is in a single place. Programmers need not worry if it is safe to load a particular object-they just make the call as normal and the subclassed method takes care of the rest. Couple this into your menu control logic and you have the potential to control your application state from a single point! You can subclass many other Visual Basic elements. I will explain how to do this in more detail later in the chapter.

Now you should have a few ideas to start with. Remember that building an application template is a task that should be treated as a project in its own right. Time and budget will need to be allocated for the task; therefore, it makes sense to pin down the requirements beforehand. The success of your template will very much depend on the thought that has gone into its design. In the following sections, I will explain how to perform some of the tasks we have described so far.

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