1. -（BOOL) isKindOfClass: <class>
判断该对象是否为<class>类或其子类的实例
2. -(BOOL) isMemberOfClass: <class>
判断该对象是否为<class>类的实例
3. -(BOOL) respondsToSelector: <selector>
判断该对象是否可响应<selector>函数
4. +(BOOL) instancesRespondToSelector: <selector>
判断该类的实例是否可响应<selector>函数
5. +(BOOL) isSubclassOfClass: <class>
判断该类是否为<class>类的子类
6. -(id) performSelector: <selector>
对该对象添加<selector>函数的实现
7. -(id) performSelector: <selector> withObject: <object>
对该对象添加<selector>函数的实现，并传入<object>参数 ？？这个参数干什么用的？？
8. -(id) performSelector: <selector> withObject: <object1> withObject: <object2>
对该对象添加<selector>函数的实现，并传入<object1>和<object2>参数