isKindOfClass: isSubclassOfClass

- (BOOL)isKindOfClass:(Class)aClass;判断是否是这个类或者这个类的子类的实例

[object isKindOfClass:[NSString class]]

- (BOOL)isMemberOfClass:(Class)aClass;判断是否是这个类的实例

[object isMemberOfClass:[NSString class]]

+ (BOOL)isSubclassOfClass:(Class)aClass; 作用与 isKindOfClass 一样，区别只是 isSubclassOfClass 是类方法， isKindOfClass 是实例方法 

[[object class] isSubclassOfClass:[NSString class]]