Weak

示例代码：

__weak NSObject *object;

{
    NSObject *object_1 = [NSObject new];
    NSLog(@"Retain Count = %ld", CFGetRetainCount((__bridge CFTypeRef)(object_1)));
    object = object_1;
    NSLog(@"Retain Count = %ld", CFGetRetainCount((__bridge CFTypeRef)(object_1)));
}

运行结果：

Retain Count = 1
Retain Count = 1

示例代码：

__strong NSObject *object;

{
    NSObject *object_1 = [NSObject new];
    NSLog(@"Retain Count = %ld", CFGetRetainCount((__bridge CFTypeRef)(object_1)));
    object = object_1;
    NSLog(@"Retain Count = %ld", CFGetRetainCount((__bridge CFTypeRef)(object_1)));
}

运行结果：

Retain Count = 1
Retain Count = 2

从上面的代码可以看出：

• weak变量无法使对象的计数器+1