什么是“代表”在Objective C的iPhone开发中？ [英] What is a "delegate" in Objective C's iPhone development?

问题描述

解决方案

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委托允许一个对象在事件发生时将消息发送到另一个对象。例如，如果您使用 NSURLConnection类。 NSURLConnection有三个常见的代理：

   - （void）connection：（NSURLConnection *）连接didFailWithError：（NSError *）错误
  - （void）connectionDidFinishLoading：（NSURLConnection *）连接
  - （void）连接：（NSURLConnection *）连接didReceiveResponse :( NSURLResponse *）响应
  

当NSURLConnection遇到失败，成功完成或从网站收到回复时，一个或多个这些代理将被调用。

What is a "delegate" in Objective C's iPhone development?

解决方案

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A delegate allows one object to send messages to another object when an event happens. For example, if you're downloading data from a web site asynchronously using the NSURLConnection class. NSURLConnection has three common delegates:

 - (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
 - (void)connectionDidFinishLoading:(NSURLConnection *)connection
 - (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response

One or more of these delegates will get called when NSURLConnection encounters a failure, finishes successfully, or received a response from the web site, respectively.

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