Composite Patterns

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So what have we wrought here? Let's take a look at the UML diagram of our to most abstract strategies.

Figure 2.8 SwitcherStrategy and MultiStrategy 

Note that the subclasses hold references to their own superclasses! 

The key to the power that lies in the SwitcherStrategy and the MultiStrategy lies in the fact that they hold references to their own superclass, IUpdateStrategy. This is what enables them to be create any behavior they want, including combinations of behaviors and dynamic modifications of behaviors. This self-referential class structure is known as the Composite Design Pattern (The Decorator pattern can be considered to be specialized form of the Composite pattern). The massive power, flexibility and extensiblility that this pattern generates warrants further, more formal study, which is where we're heading next. Stay tuned!