NSURLConnection是否保留其委托？ [英] Does a NSURLConnection retain its delegate?

问题描述

我的问题摘要：NSURLConnection是否保留其委托？

Summary of my question: Does NSURLConnection retain its delegate?

详细的问题和场景：

我有一个自定义类，名为JsonDownloader，它接收一个URL和返回URL返回的JSON的NSDictionary。

I have a custom class, called JsonDownloader that is takes in a URL and returns an NSDictionary of the JSON that the URL returns.

在iPhone应用程序上，我执行类似这样的操作。 （init方法启动整个过程）

On an iPhone app, I do something like this. (the init method kicks off the whole process)

- (void)viewDidLoad {
    JsonDownloder *temp = [[[JsonDownloader alloc] initWithURL:urlString returnDataTo:self]];
    [temp release];
    [super viewDidLoad];
}

当JsonDownloader完成下载和解析时，它会对returnDataTo执行回调：object，在这种情况下，是调用对象。

When the JsonDownloader is done downloading and parsing, it performs a callback to the returnDataTo: object, in this case, the calling object.

这很好用。即使我在我的Web服务器响应中引入了30秒的延迟，JsonDownloader仍然存在，并且正确回调。

This works just fine. Even if I introduce a 30 second delay in my web servers response, the JsonDownloader still exists and does it's callback correctly.

所以我的问题是：什么是保持JsonDownloader的方式在事件周期结束后？我明确地发布了它。

So my questions is this: What is keeping JsonDownloader way past the end of the event cycle? I am explicitly releasing it.

我的预感是NSURLConnection必须对其委托进行保留，但我没有在文档中看到任何内容。有人有想法吗？

My hunch is that NSURLConnection must do a retain on its delegate, but I didn't see anything in the documentation. Anyone have an ideas?

推荐答案

没有很多setter不会复制或保留传递给它的变量，以免当保留计数达到零时，将所述变量的内存重新分配给其他内容。

There aren't many setters that don't either copy or retain a variable being passed to it, lest the memory of said variable be re-allocated to something else when its retain count reaches zero.

然而，答案是肯定的，确实如此。一小段测试代码显示代表的保留计数上升：

However, the answer is YES, it does. A little bit of test code shows the delegate's retain count go up:

NSLog(@"Retain count before: %d", [self retainCount]);
NSURLRequest* request = [NSURLRequest requestWithURL:[NSURL URLWithString:@"http://google.com"]];
NSURLConnection* conn = [NSURLConnection connectionWithRequest:request delegate:self];
NSLog(@"Retain count after: %d", [self retainCount]);

在日志中产生：

Running…
2009-07-09 02:13:40.516 delegateRetain[45123:a0f] Retain count before: 1
2009-07-09 02:13:40.525 delegateRetain[45123:a0f] Retain count after: 2

Debugger stopped.

所以你可以清楚地看到在 connectionWithRequest：delegate：self的保留计数确实增加了+1。如果你觉得自己很勇敢并且想要使用EXC_BAD_ACCESS诸神，请加入

So you can see pretty clearly that in connectionWithRequest:delegate: "self" is indeed having its retain count increased +1. If you're feeling brave and want to mess with the EXC_BAD_ACCESS gods, add in

[conn dealloc];
NSLog(@"Retain count after dealloc: %d", [self retainCount]);

将再次打印出1，显示一个dealloc减少后的值。但是，你会得到一个很好的程序接收信号：EXC_BAD_ACCESS。因为 NSAutoreleasePool 将尝试释放连接，它将消失;）

which will print out "1" again, showing a post dealloc decrement. However, you'll get a nice Program received signal: "EXC_BAD_ACCESS". because the NSAutoreleasePool will try to release the connection and it will be gone ;)

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