ios - 在 ios 中取消 NSURLConnection

Question

我在 mapView 上调用网络服务拖动/区域更改。我想在 Web 服务调用中保持一些延迟。所以我希望每当用户多次拖动 map 时，应该取消所有以前的 Web 服务调用，并且只应该触发最后一次拖动 Web 服务调用。

我该怎么做呢？

以下是我的代码:

{ .... NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:60.0];
        [request setValue:@"application/json" forHTTPHeaderField:@"Content-Type"];
        [request setValue:@"application/json" forHTTPHeaderField:@"Accept"];

        NSString *postLength = [NSString stringWithFormat:@"%lu",(unsigned long)[data length]];

        [request setValue:postLength forHTTPHeaderField:@"Content-Length"];
        [request setHTTPBody:data];

        [request setHTTPMethod:@"POST"];
        NSMutableDictionary __block *dictResponse;
    [[NSOperationQueue mainQueue] cancelAllOperations];
        [NSURLConnection sendAsynchronousRequest:request queue:[NSOperationQueue mainQueue] completionHandler:^(NSURLResponse *response, NSData *data, NSError *connectionError) {

            if(connectionError == nil){

                dictResponse = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingMutableContainers error:&connectionError];
                }

Answer 1

您不能取消 sendAsynchronousRequest .如果您使用基于委托(delegate)的 NSURLConnection请求，那么您可以取消它，但是(a)这比您可能想要打扰的编码更多； (b) NSURLConnection已弃用，因此您应该是 NSURLSession反正; (c) NSURLSession允许您使用 NSURLSessionTask 取消任务返回给您的引用:

NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:60.0];
[request setValue:@"application/json" forHTTPHeaderField:@"Content-Type"];
[request setValue:@"application/json" forHTTPHeaderField:@"Accept"];
[request setHTTPBody:data];
[request setHTTPMethod:@"POST"];

NSURLSessionTask *task = [[NSURLSession sharedSession] dataTaskWithRequest:request completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
    if (error) {
        NSLog(@"connection error = %@", error);
        return;
    }
    NSError *parseError;
    NSDictionary *responseObject = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingMutableContainers error:&parseError];
    if (!responseObject) {
        NSLog(@"parse error = %@", parseError);
    }
    dispatch_async(dispatch_get_main_queue(), ^{
        // use response here; e.g., updating UI or model objects
    });
}];
[task resume];

如果您需要取消此请求，请调用 [task cancel] .所以保存这个 NSURLSessionTask如果您想跟踪它并稍后取消它，请在一些弱变量中。