|
|
|
|
|
|
|
Q What does a proxy class do for the application? |
|
|
|
|
|
|
|
|
A If you're developing a distributed Visual Basic application, you would have a proxy class that locally represents a remote subsystem. For example, if you deploy the Business Rules Subsystem on a workgroup server, and the Database Access Subsystem on a separate enterprise server, you might find it convenient to create a data access proxy class, DBProxy, that handles the information persistence needs of the workgroup server on behalf of the enterprise server. |
|
|
|
|
|
|
|
|
The workshop includes quiz questions to help gauge your grasp of the material. You'll find the answers to this quiz in Appendix A, Answers. Even if you feel that you understand the concepts presented here, you should work through the quiz. The last section contains exercises to help reinforce your learning. |
|
|
|
|
|
|
|
|
1. What is the compartmental hierarchy for subsystems and their members? |
|
|
|
|
|
|
|
|
2. Why are subsystem interface classes so important? |
|
|
|
|
|
|
|
|
3. What is a good way to decouple an actual form in the Graphical User Interface Subsystem from direct communications with the Database Access Subsystem? |
|
|
|
|
|
|
|
|
4. What's the importance of collections of business classes in the Business Rules Subsystem? |
|
|
|
|
|
|
|
|
5. Explain the nature of the form controller in subsystem-to-subsystem communications. |
|
|
|
|
|
|
|
|
1. Open a new Visual Basic project (Standard EXE). Create a broker class that works with the Security Subsystem in this book and a Graphical User Interface Subsystem to process the ID and password of a user. The Graphical User Interface Subsystem consists of a form, Form1, and a controller class, CForm1. |
|
|
|
|
|
|
|
|
2. Using exercise 1, create a facade class, PrinterFacade, that retrieves the hDc handle of the physical printer on behalf of CForm1. |
|
|
|
|
|