Æliens

design pattern(s) -- catalogue

• a common design vocabulary
• documentation and learning aid
• an adjunct to existing methods
• a target for redesign

see the GOF Design Patterns and the Patterns Homepage

structure

name - handle

• increases design vocabulary

problem - when to apply

• explains the problem and the conflict

solution - general arrangement

• design, responsibilities, collaborations

consequences - tradeoffs

• to understand the costs and benefits

causes for redesign

design for change

1. creating an object by specifying a class explicitly -- Abstract Factory, Factory Method, Prototype
2. dependence on specific operations Chain of Responsibilty, Command
3. dependence on hardware & software platforms -- Abstract Factory, bridge
4. dependence on object implementation or representation Abstract Factory, Bridge, Memento, Proxy
5. algorithm dependence -- Builder, Iterator, Strategy, Template Method, Visitor
6. extending functionality by subclassing -- Bridge, Chain, Composite, Decorator, Observer
7. tight coupling -- Abstract Factpry, Bridge, Chain of Responsibilities, Command, Facade, Mediator, Observer
8. inability to alter classes conveniently -- Adaptor, Decorator, Visitor

kinds of patterns

• creational patterns -- factory, singleton, ...
• structural patterns -- adaptor, composite, bridge, ...
• behavioral patterns -- mediator, observer, command, ...

see also

see UML