笔记07 msgSend

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/*
 [super message]的底层实现
 1.消息接收者仍然是子类对象
 2.从父类开始查找方法的实现
 */

struct objc_super {
    __unsafe_unretained _Nonnull id receiver; // 消息接收者
    __unsafe_unretained _Nonnull Class super_class; // 消息接收者的父类
};

- (void)run
{
    // super调用的receiver仍然是MJStudent对象
    [super run];
    
    
//    struct objc_super arg = {self, [MJPerson class]};
//
//    objc_msgSendSuper(arg, @selector(run));
//
//
//    NSLog(@"MJStudet.......");
    
}

- (instancetype)init
{
    if (self = [super init]) {
        NSLog(@"[self class] = %@", [self class]); // MJStudent
        NSLog(@"[self superclass] = %@", [self superclass]); // MJPerson

        NSLog(@"--------------------------------");

        // objc_msgSendSuper({self, [MJPerson class]}, @selector(class));
        NSLog(@"[super class] = %@", [super class]); // MJStudent
        NSLog(@"[super superclass] = %@", [super superclass]); // MJPerson
    }
    return self;
}

@end

 class  superclass 方法的底层实现
//@implementation NSObject
//
//- (Class)class
//{
//    return object_getClass(self);
//}
//
//- (Class)superclass
//{
//    return class_getSuperclass(object_getClass(self));
//}
//
//@end



//        NSLog(@"%d", [[NSObject class] isKindOfClass:[NSObject class]]);//1
//        NSLog(@"%d", [[NSObject class] isMemberOfClass:[NSObject class]]);//0
//        NSLog(@"%d", [[MJPerson class] isKindOfClass:[MJPerson class]]);//0
//        NSLog(@"%d", [[MJPerson class] isMemberOfClass:[MJPerson class]]);//0
        
        
        // 这句代码的方法调用者不管是哪个类（只要是NSObject体系下的），都返回YES
        NSLog(@"%d", [NSObject isKindOfClass:[NSObject class]]); // 1
        NSLog(@"%d", [NSObject isMemberOfClass:[NSObject class]]); // 0
        NSLog(@"%d", [MJPerson isKindOfClass:[MJPerson class]]); // 0
        NSLog(@"%d", [MJPerson isMemberOfClass:[MJPerson class]]); // 0
        
        
//        id person = [[MJPerson alloc] init];
        
//        NSLog(@"%d", [person isMemberOfClass:[MJPerson class]]);//1
//        NSLog(@"%d", [person isMemberOfClass:[NSObject class]]);//0
        
//        NSLog(@"%d", [person isKindOfClass:[MJPerson class]]);//1
//        NSLog(@"%d", [person isKindOfClass:[NSObject class]]);//1
        
        
//        NSLog(@"%d", [MJPerson isMemberOfClass:object_getClass([MJPerson class])]);//1
//        NSLog(@"%d", [MJPerson isKindOfClass:object_getClass([NSObject class])]);//1
        
//        NSLog(@"%d", [MJPerson isKindOfClass:[NSObject class]]);//1  因为 最后调用的是 元类 NSObject的superclass 的时候 指向的是 NSObject 的class 对象，最后获取到的是 [NSObject class] 对象，正好等于参数[NSObject class]

NSObject  底层 实现
- (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;
}


+ (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;
}




NSObject *obj2 = [[NSObject alloc]init];

  id cls = [MJPerson class];

    void *obj = &cls;

    [(__bridge id)obj print];
/*
 1.print为什么能够调用成功？
 
 2.为什么self.name变成了ViewController等其他内容
 */

内存结构

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相当于 _name 的预期地址和 obj2 的地址 重合了