Runtime：isMemberOfClass与isKindOf

夜景

目录
一，实例方法
二，类方法

一，实例方法

1，实例代码

Person *person = [Person new];
NSLog(@"%d", [person isMemberOfClass:[Person class]]);
NSLog(@"%d", [person isMemberOfClass:[NSObject class]]);
NSLog(@"%d", [person isKindOfClass:[Person class]]);
NSLog(@"%d", [person isKindOfClass:[NSObject class]]);

// 打印
1
0
1
1

2，底层代码（源码下载地址）

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

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

3，说明

• isMemberOfClass：该实例对象是否属于某个类

• isKindOfClass：该实例对象是否属于某个类或其子类

二，类方法

1，实例代码

NSLog(@"%d", [Person isMemberOfClass:[Person class]]);
NSLog(@"%d", [Person isMemberOfClass:[NSObject class]]);
NSLog(@"%d", [Person isKindOfClass:[Person class]]);
NSLog(@"%d", [Person isKindOfClass:[NSObject class]]);

// 打印
0
0
0
1

2，底层代码

// self是class对象，object_getClass(self)是meta-class对象

+ (BOOL)isMemberOfClass:(Class)cls {
    return object_getClass((id)self) == cls;
}

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

3，说明

• isMemberOfClass：该类是否等于某个类

• isKindOfClass：该类是否等于某个类或其子类

4，分析

• 方法内部是用meta-class对象进行判断的，而传进去的是class对象，所以前三个都是0，必须传meta-class对象才能得到正确的结果

NSLog(@"%d", [Person isMemberOfClass:object_getClass([Person class])]);
NSLog(@"%d", [Person isMemberOfClass:object_getClass([NSObject class])]);
NSLog(@"%d", [Person isKindOfClass:object_getClass([Person class])]);

// 打印
1
0
1

• 第四个虽然传的是class对象，但Person的meta-class对象通过superclass指针可以找到NSObject的class对象，所以结果是1

superclass指针