iOS isKindOfClass與isMemberOfClass的區別

先看一下官方文檔的說法

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.
//調用者是給定類的實例或者是給定類的子類的實例

isMemberOfClass: Returns a Boolean value that indicates 
whether the receiver is an instance of a given class.
//調用者是不是給定類的實例
複製代碼

而後看一道題目：

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]];

複製代碼

答案是：YES / NO / NO / NO

協議有一套類方法的隱藏實現，因此編譯運行正常； 因爲NSObject meta class的父類爲NSObject class，因此只有第一句爲YES 看一下圖就明白了：