staticNSOperationQueue * queue;
- (void)viewDidLoad
{
[superviewDidLoad];
queue = [[NSOperationQueuealloc] init];
NSInvocationOperation * op = [[NSInvocationOperationalloc] initWithTarget:selfselector:@selector(download) object:nil];
[queueaddOperation:op];
}
- (void)download {
NSURL * url = [NSURLURLWithString:@"http://www.youdao.com"];
NSError * error;
NSString * data = [NSStringstringWithContentsOfURL:url encoding:NSUTF8StringEncodingerror:&error];
if (data != nil) {
[selfperformSelectorOnMainThread:@selector(download_completed:) withObject:data waitUntilDone:NO];
} else {
NSLog(@"error when download:%@", error);
queue = nil;
}
}
- (void) download_completed:(NSString *) data {
NSLog(@"call back");
self->contentLabel.text = data;
queue = nil;
}