Objective-C中的混合块和代表 [英] Mixing Blocks and Delegates in Objective-C

问题描述

当委托人收到消息时是否可以运行一个块?

Is it possible to run a block when a delegate receives a message?

例如，如果我有一个框架，该框架以void块作为参数(我们将其称为成功"块)，并且在接收到以下消息时正在使用NSURLConnection委托来处理那些方法参数:来自网页的响应，如何调用方法参数中传递的成功"块?

For example, if I had a framework that took a void block as a parameter (we'll call it the "success" block), and was using an NSURLConnection delegate to do stuff with those method arguments, when I receive a response from the webpage, how can I call the "success" block passed in the method parameters?

这对我来说很难做到，而且我显然没有任何代码，但是我可以澄清您是否有任何疑问.

This is really hard for me to explain, and I obviously don't have any code for this, but I can clarify if you have any questions.

推荐答案

您绝对可以.这就是所有完成处理程序/回调的工作方式.实际上，这就是 的一个块.

You absolutely can. That is how all completion handlers / callbacks work. In fact, that is what a block is for.

举一个简单的例子，考虑以下NSURLConnection类方法:

To take a simple example, consider this NSURLConnection class method:

+ (void)sendAsynchronousRequest:(NSURLRequest *)request
                          queue:(NSOperationQueue *)queue
              completionHandler:(void (^)(NSURLResponse *response,
                                          NSData *data,
                                          NSError *connectionError))handler

对于第三个参数，您传递了一个块.当请求结束后，在将来的某个时间，NSURLConnection会做什么?它会调用该块.

For the third parameter, you pass a block. And when the request is all over, some time in the future, what does NSURLConnection do? It calls the block.

因此，您可以执行与NSURLConnection完全相同的操作.您可以编写一个占用一个块的方法，按住该块，执行可能要花费一些时间的操作，然后稍后调用该块.

So, you can do exactly the same that NSURLConnection is doing. You can write a method that takes a block, you hold on to the block, you do something that perhaps takes some time, and then later you call the block.

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