對weak的了解

參考文章：http://blog.cocoachina.com/article/61909

__weak typeof(self) weakSelf = self;
           

weak不會使strongSelf的引用計數增加，而是把strongSelf對象指針（weakSelf和strongSelf指針相同）加到了weak的hash表中，以便後續使用weakSelf時能找到

測試代碼如下：

- (void)test{
    TPLog(@"self === %@", self);
    typeof(self) strongSelf = self;
    TPLog(@"strong self === %@", strongSelf);
    __weak typeof(self) weakSelf = self;
    TPLog(@"weak self === %@", weakSelf);
}
           

列印結果為：

2019-02-22 23:41:19.771670+0800 TPWeiShangTool[17537:832581] self === <AppDelegate: 0x60000141c8c0>
2019-02-22 23:41:19.771817+0800 TPWeiShangTool[17537:832581] strong self === <AppDelegate: 0x60000141c8c0>
2019-02-22 23:41:39.853423+0800 TPWeiShangTool[17537:832581] weak self === <AppDelegate: 0x60000141c8c0>
           

可見strongSelf和weakSelf的位址相同