先看一下官方文件的說法
isKindOfClass: Returns a Boolean value that indicates whether the receiver is
an instance of given class or an instance of any class that inherits from that class.
//呼叫者是給定類的例項或者是給定類的子類的例項
isMemberOfClass: Returns a Boolean value that indicates
whether the receiver is an instance of a given class.
//呼叫者是否是給定類的例項
複製程式碼然後看一道題目：
BOOL res1 = [(id)[NSObject class] isKindOfClass:[NSObject class]];
BOOL res2 = [(id)[NSObject class] isMemberOfClass:[NSObject class]];
BOOL res3 = [(id)[xxObj class] isKindOfClass:[xxObj class]];
BOOL res4 = [(id)[xxObj class] isMemberOfClass:[xxObj class]];
複製程式碼答案是：YES / NO / NO / NO
協議有一套類方法的隱藏實現，所以編譯執行正常； 由於NSObject meta class的父類為NSObject class，所以只有第一句為YES 看一下圖就明白了：