问题描述
我最近在使用Facebook的应用程序切换功能时遇到了一个问题. Facebook登录后，我需要调用一个阻止程序.
I recently met a problem using blocks with Facebook's app switching. I needed to call a block after the Facebook login.
首先，当应用切换回去时，我的区块被破坏了(因为它在堆栈中)，所以我决定保留它.但这没有用，我搞砸了这个问题:/.我在该博客和此处.
First my block was destroyed when the app switched back ('cause it was on the stack), so I decided to retain it. But that didn't work, and I messed with that problem :/. I found a solution on that blog and also here.
我的问题很简单:为什么复制有效，但保留无效?
推荐答案
由于创建块时，没有要保留的内容，因为直到使用Block_copy将其复制到堆中为止，堆中都不存在该块. WWDC关于块的讲座对此进行了介绍.
Because when you create a block there is nothing to retain, since it doesn't exist in the heap until you copy it there with Block_copy. This is covered in the WWDC lectures about blocks.
更多信息: http://www.friday. com/bbum/2009/08/29/blocks-tips-tricks/
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