这两个方法都有实例方法和类方法
实例方法内部：调用者的类对象 == 传进去的 cls
类方法内部：调用者的元类的对象 == 传进去的 cls

源码：

- (BOOL)isKindOfClass:(Class)cls {
    // 当前类对象 == cls 或 cls子类
    for (Class tcls = [self class]; tcls; tcls = tcls->superclass) {
        if (tcls == cls)
            return YES;
    }
    return NO;
}

- (BOOL)isMemberOfClass:(Class)cls {
    // 当前类对象 == cls
    return [self class] == cls
}


+ (BOOL)isKindOfClass:(Class)cls {
    // 当前元类对象 == cls 或 cls子类
    for (Class tcls = object_getClass(self); tcls; tcls = tcls->superclass) {
        if (tcls == cls)
            return YES;
    }
    return NO;
}

+ (BOOL)isMemberOfClass:(Class)cls {
    // 当前元类对象 == cls
    return object_getClass(self) == cls
}

即：

[对象 isKindOfClass:类对象];
[类对象 isKindOfClass:元类对象];

[对象 isMemberOfClass:类对象];
[类对象 isMemberOfClass:元类对象];

但是，如果 [类对象 isKindOfClass:[NSObject class]]; == YES
因为：子类的元类对象的 superclas->superclass->superclass ... 基类的类对象

面试题

1、以下两组代码的打印结果？

BOOL re1 = [[NSObject class] isKindOfClass:[NSObject class]]; // YES
BOOL re2 = [[NSObject class] isMemberOfClass:[NSObject class]]; // NO
BOOL re3 = [[Person class] isKindOfClass:[Person class]]; // NO
BOOL re4 = [[Person class] isMemberOfClass:[Person class]]; // NO

BOOL re5 = [[NSObject alloc] isKindOfClass:[NSObject class]]; // YES
BOOL re6 = [[NSObject alloc] isMemberOfClass:[NSObject class]]; // YES
BOOL re7 = [[Person alloc] isKindOfClass:[Person class]]; // YES
BOOL re8 = [[Person alloc] isMemberOfClass:[Person class]]; // YES