Revision Notes/Design Patterns
Field Entry - Design Patterns
Decorator Pattern
Wraps an object to add new behaviors dynamically at runtime without modifying the original class or creating a huge number of subclasses.
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Field Note - Real-world Analogy
“Think of dressing up for different weather. You start with your base outfit (the original object). Cold outside? Wrap a jacket on top (Decorator 1). Raining? Add a raincoat on top of that (Decorator 2). You're still you underneath — just with extra layers added dynamically.”
Field Observations - Key Topics Covered
The problem: you want to add optional features to an object. With inheritance you'd create subclasses for every combination: PlainCoffee, CoffeeWithMilk, CoffeeWithSugar, CoffeeWithMilkAndSugar, CoffeeWithVanilla... this explodes combinatorially. The Decorator pattern avoids this entirely.
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See Also in Design Patterns