Design Patterns

What are design patterns? A general reusable solution to a commonly occurring problem. A description or template for how to solve a problem that can be used in many different situations.

For example…

Gang of Four

Words to live by Program to an interface, not an implementation. Favor object composition over class inheritance. Interfaces: good Inheritance: bad

Types of design patterns Creational –Instantiation of objects Structural –Class and object composition Behavioral –Communication between objects

Creational patterns Abstract Factory Builder Factory Method Prototype Singleton

Creational patterns Abstract Factory Builder Factory Method Prototype Singleton

Structural patterns Adapter Bridge Composite Decorator Façade Flyweight Proxy

Structural patterns Adapter Bridge Composite Decorator Façade Flyweight Proxy

Behavioral patterns Chain of responsibility Command Interpreter Iterator Mediator Memento Observer State Strategy Template method Visitor

Behavioral patterns Chain of responsibility Command Interpreter Iterator Mediator Memento Observer State Strategy Template method Visitor

And this affects me how? What are design patterns used for? What are the three categories of GoF design patterns? Patterns you should be able to describe –Singleton –Composite –Façade –Chain-of-responsibility –Observer