NSObject 对象的真正架构

NSObject 其实 实现了 NSObject协议，并不像java里的 Object 类一样。此协议定义了如下方法：

Identifying Classes

• – class  required method
• – superclass  required method

Identifying and Comparing Objects

• – isEqual:  required method
• – hash  required method
• – self  required method

Managing Reference Counts

• – retain  required method
• – release  required method
• – autorelease  required method
• – retainCount  required method

Testing Object Inheritance, Behavior, and Conformance

• – isKindOfClass:  required method
• – isMemberOfClass:  required method
• – respondsToSelector:  required method
• – conformsToProtocol:  required method

Describing Objects

• – description  required method

Sending Messages

• – performSelector:  required method
• – performSelector:withObject:  required method
• – performSelector:withObject:withObject:  required method

Determining Allocation Zones

• – zone  required method

Identifying Proxies

– isProxy  required method