runtime - 面试题系列2 - isKindOf 和isMemberOf,isSubclassOf

这两者直接看源码就好了,在NSObject.mm这个文件里面

+ (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;
}

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

这就是五个定义,可以看的出来isMember就是判断是否是当前类,而isKindOf和isSubclassOfClass会考虑是否是父类

 Person *person = [[Person alloc] init];
 NSLog(@"%d",[person isKindOfClass:[Person class]]);      //1
 NSLog(@"%d",[person isKindOfClass:[NSObject class]]);    //1
 NSLog(@"%d",[person isMemberOfClass:[Person class]]);    //1
 NSLog(@"%d",[person isMemberOfClass:[NSObject class]]);  //0
 NSLog(@"%d",[Person isSubclassOfClass:[Person class]]);  //1
 NSLog(@"%d",[Person isSubclassOfClass:[NSObject class]]);//1

所以如果只想判断是否是Person就用isMember,如果是它的父类也行就用其它两个