# block 原理

1. 解决循环引用不应该使用 weakself，而是使用 strong-weak
```Objective-c
__weak typeof(self) Weakself = self;
self.block = ^ {
    __strong typeof(Weakself) Strongself = Weakself;
    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(2 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^ {
        NSLog(@"%@", Strongself.name);
    });
};
self.block();
```

![image-20200810214301251](/Users/lbp/Library/Application Support/typora-user-images/image-20200810214301251.png)



字节对齐：k值：8的倍数。

字节对齐的原因：