Chapter 29. The State Pattern

The State pattern is used when you want to have an object represent the state of your application and switch application states by switching objects. For example, you could have an enclosing class switch between a number of related contained classes and pass method calls on to the current contained class. Design Patterns suggests that the State pattern switches between internal classes in such a way that the enclosing object appears to change its class. In VB, at least, this is a bit of an exaggeration, but the actual purpose to which the classes are applied can change significantly.

Many programmers have had the experience of creating a class that performs slightly different computations or displays different information ...

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