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178: Set objNewMember = Nothing
179: End Sub
180: |
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Interfacing Between the Internal Application Manager Subsystem and All Subsystems |
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Notice in Listing 20.4 how the Internal Application Manager Subsystem controls the initialization of the system. It's also actively involved in tracking state changes that applications typically go through. In any subsystem in which you expect a class to affect the state of another subsystem, it's advisable to include this subsystem in the actual tracking and recording of such changes. |
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Identifying the Need for Other Subsystems |
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So far, you have been introduced to many critical application subsystems that all Visual Basic applications require in order to be useful to the user and easily maintained by you, the developer. However, the list of all possible subsystems you might need isn't complete. |
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For instance, you might need a help subsystem that would be responsible for implementing user help for the application. You might also create an application setup subsystem to handle installation and configuration issues, particularly if you use an API for custom installations. In a broader sense, there are those industry-specific subsystems that have proven elusive to standardize in any one book. The development of these subsystems is the challenge you are presented with. |
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Although it's difficult to document industry-standard subsystems, there are some interesting projects by major software manufacturing companies in this area. Microsoft has been pushing its COM solutions (along with SAP business components) towards industry-specific subsystems. Sun Microsystems has also gone after this previously neglected market. Most notable of all, though, is IBM's San Francisco project. It is based on Java, but the design patterns and object interactions embodied in the project can be adapted to Visual Basic or accessed via COM-Java bridges. For more information on the San Francisco project, visit www.ibm.com/java/sanfrancisco. |
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