containsObject:和NSSet的成员:方法之间的区别？

Question

属于NSSet类的这两个方法之间的区别是什么:

-(BOOL)containsObject:(id)anObject
-(id)member:(id)object 

Answer 1

答案在于返回值.containsObject返回YES或NO,具体取决于您发送的对象是否属于该特定集.

成员返回id,这意味着如果该对象是该集合的一部分,它将返回实际对象.

例如,您有一个带有anObject的NSSet,aSet.anObject属于该集合.

[aSet containsObject:anObject]; //returns YES
[aSet member:anObject]; //If the set contains an object equal to object (as determined by isEqual:) then that object (typically this will be object), otherwise nil.

如果aSet中不存在anObject:

[aSet containsObject:anObject]; //return NO
[aSet member:anObject]; //return nil