object composition (Decorator pattern) is often a better technique than subclassing for extending class behavior.

1.Abstract Factory

provides an interface for creating families of related or dependent objects without specifying their concrete classes

提供接口创建相同或类似的对象，不需要指定其具体的类型

iso中主要体现在NSNumber和NSArray和NSString以及NSDcitionary上

2.Adapter

The Adapter design pattern converts the interface of a class into another interface that clients expect

将一个类的接口准确转换成clinet期望的一个接口，主要使用协议

3.Chain of Responsibility

The Chain of Responsibility design pattern decouples the sender of a request from its receiver by giving more than one object a chance to handle the request.

责任链主要将请求的发送者和接收者解耦

ios中主要体现在响应者链上

An instance of the class encapsulates an Objective-C message

4.Command

The Command design pattern encapsulates a request as an object, thereby letting you parameterize clients with different requests, queue or log requests, and support undoable operations

命令设计模式封装了对象的要求，从而让你的参数适应client不同的要求，排队或记录请求日志，支持撤消操作

ios上主要体现在NSInvocation上面