ActionScript 3.0 Design Patterns

An open triangle on a line from a child class to the parent class indicates the inheritance symbol in Design Pattern class diagrams. In the Participant Relations diagram above, you can see symbols for both single and multiple inheritance in red. Inheritance in design patterns is so common, pointing out which designs do not use inheritance is easier than listing all of the ones that do. Those pattens that have no inheritance in their design include:

• Singleton
• Facade
• Memento

So when thinking about inheritance, you can begin by thinking design patterns because most include some kind of inheritance in the relations between pattern participants.

But I thought they said…

You’re probably thinking that a key principle for design patterns is to favor object composition over class inheritance, and here we find that the Gang of Four is using inheritance in all but three of their design patterns. What’s up with that?

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