Advanced ActionScript 3 with Design Patterns

Chapter 9. Decorator Pattern

<feature><title>In This Chapter</title>

• Understanding the Decorator Pattern 114

• Building Reader Decorators 117

• Building Visual and Commutative Decorators 128

• Summary 136

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The Decorator pattern enables you to apply new behavior to an object at runtime. Traditionally, many developers learn to add behavior by using inheritance rather than composition. This means that if you want to add a move() method to an existing Widget class, you’d extend Widget to define a new MovableWidget class. Or, if you want to redefine the move() method of MovableWidget so that it moves only until its fuel is used up, you could extend MovableWidget to define FuelableMovableWidget.

However, inheritance has two major drawbacks in such cases: ...