转 NSOperation和NSURLConnection

最近一个客户向我汇报了一个程序的问题。经过分析发现问题是NSURLConnection没有正常工作。记得以前测试时没有问题啊。后来上网查到 原来在iOS 4.0以后，NSURLConnection无法在NSOperation中正常运行，换句话说，NSURLConnection只能运行于主线程。解决 方法其实倒是蛮简单（比如我的程序在download中）：

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-(void)download { // NSURLConnectionn won't work if it's not in the main thread if (![NSThread isMainThread]) { [self performSelectorOnMainThread:@selector(download) withObject:nil waitUntilDone:NO]; return; } NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:_urlString]]; _connection = [[NSURLConnection alloc] initWithRequest:request delegate:self]; }