NSURLCache 在 iOS 4 中如何工作？

发布于 2024-11-15 15:38:08 字数 1378 浏览 2 评论 0原文

当我学习 NSURLCache 文档时，我找不到很多重要的注释。我发现网络中的许多主题抱怨使用 NSURLCache 的 NSURLConnection 存在内存泄漏。当我尝试为 iOS 4.3 编写一些应用程序时，我发现 MSURLCache 有一些奇怪的行为。

在application:didFinishLaunchingWithOptions:中，我设置内存容量为10MB的NSURLCache实例，初始化 NSURLRequest 与 NSURLRequestUseProtocolCachePolicy 但我无法接收我的 NSURLConnection 委托中的 connection:willCacheResponse: 消息。当我检查应用程序不同点的内存容量时，它是 0MB。为什么？ Apple 是否可以通过将 NSURLCache 内存容量设置为 0 来修复一些内存泄漏？我创建了自定义 NSURLCache 并通过以下方式重写了 setMemoryCapacity: 方法：

-(void)setMemoryCapacity:(NSUInteger)memoryCapacity {
    if (memoryCapacity > 0) {
        [super setMemoryCapacity:memoryCapacity];
    }
    else {
        NSLog(@"zero here");
    }
}

然后我开始调试。我的应用程序中有一些输入文本，用户在其中输入一些网址。新的 setMemoryCapacity: 方法已被调用两次：在我的应用程序委托中，当我将容量设置为 10MB 时，以及（非常有趣）当用户将焦点设置为文本输入时（参数内存容量 为 0，我在日志中收到“此处为零”字符串）。之后，我收到了发送给 NSURLConnection 委托的 connection:willCacheResponse: 消息。这很奇怪。我不明白为什么。我在手册中找不到有关此的内容。你有什么想法吗？

原文

When I learn NSURLCache documentation I can't find many important notes.
I found that many topics in web complain that NSURLConnection that use NSURLCache had memory leaks. When I tried to write some application for iOS 4.3 I found that MSURLCache have some strange behavior.

In application:didFinishLaunchingWithOptions: I set instance of NSURLCache with memory capacity 10MB, init NSURLRequest with NSURLRequestUseProtocolCachePolicy but I can't recieve connection:willCacheResponse: message in my NSURLConnection delegate. When I checked memory capacity in different points of my application, it was 0MB. Why? May be Apple fix some memory leaks by setting NSURLCache memory capacity to 0? I created custom NSURLCache and overrided setMemoryCapacity: method by this:

-(void)setMemoryCapacity:(NSUInteger)memoryCapacity {
    if (memoryCapacity > 0) {
        [super setMemoryCapacity:memoryCapacity];
    }
    else {
        NSLog(@"zero here");
    }
}

Then I started to debug. There is some input text in my app, where user put some url. New setMemoryCapacity: method has been called twice: in my app delegate, when I set capacity to 10MB and (it is very interesting) when user set focus to text input (parameter of memoryCapacity was 0 and I recieve "zero here" string in log). After that I recieved connection:willCacheResponse: messages to NSURLConnection delegate.
It was very strange. I can't understand why. I can't find things in manual about this. Do you have some thoughts?