创建和取消NSURLConnection

Question

当我允许加载完成时,我有一个NSURLConnection正常工作.但是如果用户点击后退按钮,意味着webview将消失,我想取消正在进行的NSURLConnection.但是如果在调用viewWillDissapear时调用webview,那么我会:

[conn cancel]

我得到一个NSINValidArgument异常.

连接被定义为.h文件中的实例数据:

NSURLConnection *conn;

异步是在这里启动的:

NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:articleURL]];

    if ([NSURLConnection canHandleRequest:request] && reachable) {
        // Set up an asynchronous load request
        conn = [NSURLConnection connectionWithRequest:request delegate:self];
        loadCancelled = NO;
        if (conn) {
            NSLog(@" ARTICLE is REACHABLE!!!!");
            self.articleData = [NSMutableData data];
        }
    }

Answer 1

你得到异常的原因是你将autorelease对象保存到实例变量.
当用户单击后退按钮时,"conn"将立即自动释放.之后,你打电话取消.因此,你有例外.
要防止这种情况,您应该在将NSURLConnection对象保留在实例变量中时保留它.

conn = [[NSURLConnection connectionWithRequest:request delegate:self] retain];

要么

conn = [[NSURLConnection alloc] initWithRequest:request delegate:self];

不要忘记在dealloc方法中释放它.