ASIHTTPRequest / ASIFormDataRequest - 在ARC下的块内引用请求对象 [英] ASIHTTPRequest / ASIFormDataRequest - referencing request object within blocks under ARC

问题描述

非常类似于这个问题，我正在尝试转换使用 ASIHTTPRequest &的项目。 ASIFormDataRequest 到ARC。

Very similar to this question, I am trying to convert a project that uses ASIHTTPRequest & ASIFormDataRequest to ARC.

在我的视图控制器类中，我经常在完成块中引用并使用请求对象的属性（查看响应代码，响应数据等）：

In my view controller classes, I often refer to and use properties of the request object in the completion blocks (looking at the response code, response data etc):

__block  ASIFormDataRequest *request = [ASIFormDataRequest requestWithURL:[NSURL URLWithString:SOME_URL]];    
[request setCompletionBlock:^{   

    if([request responseStatusCode] == 200) ....etc

转换为ARC时，我收到警告：

When converting to ARC I get the warning:

在此强烈捕获'请求'阻止可能导致
保留周期

Capturing 'request' strongly in this block is likely to lead to a retain cycle

这样做的正确方法是什么？

What is the proper way to do this?

另一个SO用户在上一个帖子中注意到，只需添加 __ weak 就可能导致请求在完成之前被释放块，我认为是真的。

Another SO user notes in the previous thread that simply adding __weak may cause the request to be released before the completion of the block, which I believe to be true.

如何在ARC下的完成/失败块中正确引用这些属性？

How can I properly reference these properties in completion/failure blocks under ARC?

推荐答案

（我读了你对其他问题的评论）

(I read your comment to the other question)

用<$实现了几个模块之后c $ c> ASIHTTPRequest ，我了解到最好的方法是保持对您的请求对象的 strong 引用。在您的情况下，您可以这样做：

After implementing a few more modules using ASIHTTPRequest, I learned that the best way was to keep a strong reference to your request object. In your case, you can do:

self.request = [ASIFormDataRequest requestWithURL:[NSURL URLWithString:SOME_URL]];
__weak ASIFormDataRequest *weakRequest = self.request; // __block directive not needed since we only access the instance's properties. 
[self.request setCompletionBlock:^{   

    if([weakRequest responseStatusCode] == 200)
    // ...

这样你甚至可以在启动请求后控制 self.request （例如取消）。当你准备好发布你的请求时，你可以做 self.request = nil; ，可能在你的完成块内或 self.request 的父对象的清理方法。

This way you can still control self.request even after you start the request (e.g. for cancelling). You can do self.request = nil; when you're ready to release your request, maybe inside your completion block or self.request's parent object's cleanup methods.

更新：

如果您的目标是iOS 5之前的版本，那么共同点就是：使用 __ unsafe_unretained 而不是 __弱。这没关系，因为查看 ASIHTTPRequest.m ，这些块 nil '在其 dealloc（）（即它们不应该被执行）。虽然我还没有测试过，所以请确保仍然启用NSZombies进行测试。

If you're targeting pre-iOS 5, then the common ground stands: use __unsafe_unretained instead of __weak. This is OK because looking at ASIHTTPRequest.m, the blocks are nil'ed out in its dealloc() (i.e. they shouldn't get executed). Although I haven't tested that yet, so make sure to still test with NSZombies enabled.

注意：

取消 ASIHTTPRequest 对象的唯一安全方法是调用其 clearDelegatesAndCancel 方法。当我刚刚使用普通的取消一个时，我被一些讨厌的错误所困扰。

The only safe way to cancel an ASIHTTPRequest object is to call its clearDelegatesAndCancel method. I've been bitten by some nasty bugs when I was just using the plain cancel one.

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