探索 isKindOf 与isMemberOf

isKindOf 与isMemberOf

问：最终输出的结果是什么？

BOOL re1 = [(id)[NSObject class] isKindOfClass:[NSObject class]];       //
BOOL re2 = [(id)[NSObject class] isMemberOfClass:[NSObject class]];     //
BOOL re3 = [(id)[Person class] isKindOfClass:[Person class]];       //
BOOL re4 = [(id)[Person class] isMemberOfClass:[Person class]];     //
NSLog(@" re1 :%hhd\n re2 :%hhd\n re3 :%hhd\n re4 :%hhd\n",re1,re2,re3,re4);

BOOL re5 = [(id)[NSObject alloc] isKindOfClass:[NSObject class]];       //
BOOL re6 = [(id)[NSObject alloc] isMemberOfClass:[NSObject class]];     //
BOOL re7 = [(id)[Person alloc] isKindOfClass:[Person class]];       //
BOOL re8 = [(id)[Person alloc] isMemberOfClass:[Person class]];     //
NSLog(@" re5 :%hhd\n re6 :%hhd\n re7 :%hhd\n re8 :%hhd\n",re5,re6,re7,re8);

isKindOfClass

打开objc源码查看

类方法

当前类的元类（父元类，根元类，根类）是否与cls相等

+ (BOOL)isKindOfClass:(Class)cls {
    for (Class tcls = self->ISA(); tcls; tcls = tcls->superclass) {
        if (tcls == cls) return YES;
    }
    return NO;
}

实例方法

判断当前类（父类、根类）是否与cls相等

- (BOOL)isKindOfClass:(Class)cls {
    for (Class tcls = [self class]; tcls; tcls = tcls->superclass) {
        if (tcls == cls) return YES;
    }
    return NO;
}

底层实现

类似于alloc方法，isKindOfClass直接调用到了objc_opt_isKindOfClass

BOOL
objc_opt_isKindOfClass(id obj, Class otherClass)
{
#if __OBJC2__
    if (slowpath(!obj)) return NO;
    Class cls = obj->getIsa();
    if (fastpath(!cls->hasCustomCore())) {
        for (Class tcls = cls; tcls; tcls = tcls->superclass) {
            if (tcls == otherClass) return YES;
        }
        return NO;
    }
#endif
    return ((BOOL(*)(id, SEL, Class))objc_msgSend)(obj, @selector(isKindOfClass:), otherClass);
}

isMemberOfClass

类方法

判断当前的元类是否与cls相等

+ (BOOL)isMemberOfClass:(Class)cls {
    return self->ISA() == cls;
}

实例方法

判断当前类是否与cls相等

- (BOOL)isMemberOfClass:(Class)cls {
    return [self class] == cls;
}

结果

re1 :1
re2 :0
re3 :0
re4 :0

re5 :1
re6 :1
re7 :1
re8 :1