OC之runtime的(isKindOfClass和isMemberOfClass)

写如下代码:

BOOL flag1 = [[NSObject class] isKindOfClass:[NSObject class]];
BOOL flag2 = [[NSObject class] isMemberOfClass:[NSObject class]];
BOOL flag3 = [[LBPerson class] isKindOfClass:[LBPerson class]];
BOOL flag4 = [[LBPerson class] isMemberOfClass:[LBPerson class]];
NSLog(@"%d %d %d %d", flag1, flag2, flag3, flag4);

打印结果如下:

1 0 0 0

在objc中拿到isKindOfClass和isMemberOfClass的实现代码如下:

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

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

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

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

观察源码可以看出,isMemeberOfClass类方法取的的消息接收者的父类与后者相比较，是否相等

isKindOfClass类方法会取消息接受者的父类，直到取到NSObject比较，判断的是消息接收者的父类是不是后者的父类或者元类，到NSObject结束

同样的是两者的对象方法取得是接受者的类对象相比较