| -(BOOL) isKindOfClass: classObj | is object a descendent or member of classObj 此对象是否是 classObj 的子孙或一员 |
| -(BOOL) isMemberOfClass: classObj | is object a member of classObj 此对象是否是 classObj 的一员 |
| -(BOOL) respondsToSelector: selector | does the object have a method named specifiec by the selector 此对象是否有叫做selector 的 method |
| +(BOOL) instancesRespondToSelector: selector | does an object created by this class have the ability to respond to the specified selector 此对象是否是由有能力响应指定 selector 的对象所产生 |
| -(id) performSelector: selector | invoke the specified selector on the object 唤起此对象的指定selector |