JSON异步请求 [英] JSON async request

问题描述

我想使用async req来获取json数据，我已经通过syncrouns进行了此操作，但是现在要求已更改，但是我无法将此代码修改为aync，因为我必须返回NSdata

i want to use async req to get json data, i am doing this by syncrouns already, but now requirement is change, but i am unable to modify this code to aync, beacuse i have to return NSdata

+ (NSString *)stringWithUrl:(NSURL *)url
{

//    if(kShowLog)
        NSLog(@"%@", url);

    NSURL *newURL = [NSURL URLWithString:[NSString stringWithFormat:@"%@",url]];

    NSURLRequest *urlRequest = [NSURLRequest requestWithURL:newURL
                                                cachePolicy:NSURLRequestReloadIgnoringCacheData
                                            timeoutInterval:1];
    // Fetch the JSON response
    NSData *urlData;
    NSURLResponse *response;
    NSError *error;
//    NSOperationQueue *opQueue;

    // Make synchronous request
    urlData = [NSURLConnection sendSynchronousRequest:urlRequest returningResponse:&response error:&error];
    return [[NSString alloc] initWithData:urlData encoding:NSUTF8StringEncoding];
}

推荐答案

您必须为此过程创建一个单独的线程，获取json数据的同步调用将阻塞您的主线程.

You have to create a separate thread for this process, Synchronous call of getting json data will block your main thread.

我正在更改您的代码以执行异步操作，以从Web服务获取json数据.

I'm changing your code to do asynchronous operation for getting json data from web service.

+ (void)stringWithUrl:(NSURL *)url
{

 dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0ul);
 dispatch_async(queue, ^{

    //    if(kShowLog)
    NSLog(@"%@", url);

    NSURL *newURL = [NSURL URLWithString:[NSString stringWithFormat:@"%@",url]];

    NSURLRequest *urlRequest = [NSURLRequest requestWithURL:newURL
                                                cachePolicy:NSURLRequestReloadIgnoringCacheData
                                            timeoutInterval:1];
    // Fetch the JSON response
    NSData *urlData;
    NSURLResponse *response;
    NSError *error;
    //    NSOperationQueue *opQueue;

    // Make synchronous request
    urlData = [NSURLConnection sendSynchronousRequest:urlRequest returningResponse:&response error:&error];

    dispatch_sync(dispatch_get_main_queue(), ^{

        //Here you have to put your code, which you wanted to get executed after your data successfully retrived.
        //This block will get executed after your request data load to urlData.
    });

 });

}

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