详解iOS中多个网络请求的同步问题总结

- (id)initWithRequestArray:(NSArray )requestArray {
  self = [super init];
  if (self) {
    _requestArray = [requestArray copy];
    _finishedCount = 0;
    for (YTKRequest req in _requestArray) {
      if (![req isKindOfClass:[YTKRequest class]]) {
        YTKLog(@"Error, request item must be YTKRequest instance.");
        return nil;
      }
    }
  }
  return self;
}

- (void)requestFinished:(YTKRequest *)request {
  _finishedCount++;
  if (_finishedCount == _requestArray.count) {
    [self toggleAccessoriesWillStopCallBack];
    if ([_delegate respondsToSelector:@selector(batchRequestFinished:)]) {
      [_delegate batchRequestFinished:self];
    }
    if (_successCompletionBlock) {
      _successCompletionBlock(self);
    }
    [self clearCompletionBlock];
    [self toggleAccessoriesDidStopCallBack];
    [[YTKBatchRequestAgent sharedInstance] removeBatchRequest:self];
  }
}

- (void)requestFailed:(YTKRequest )request {
  [self toggleAccessoriesWillStopCallBack];
  // Stop
  for (YTKRequest req in _requestArray) {//遍历请求实例数组
    [req stop];//停止请求
  }
  // Callback  //回调
  if ([_delegate respondsToSelector:@selector(batchRequestFailed:)]) {
    [_delegate batchRequestFailed:self];
  }
  if (_failureCompletionBlock) {
    _failureCompletionBlock(self);
  }
  // Clear
  [self clearCompletionBlock];
  [self toggleAccessoriesDidStopCallBack];
  [[YTKBatchRequestAgent sharedInstance] removeBatchRequest:self];
}

- (void)loadRequest1
{
  dispatch_group_t dispatchGroup = dispatch_group_create();
  dispatch_group_enter(dispatchGroup);
  [MALAFNManger getDataWithUrl:Url1 parameters:nil finish:^(RequestResult result) {
    NSLog(@"第一个请求完成");
    dispatch_group_leave(dispatchGroup);
  } des:@"第一个url"];
  dispatch_group_enter(dispatchGroup);
  [MALAFNManger getDataWithUrl:Url2 parameters:nil finish:^(RequestResult result) {
    dispatch_async(dispatch_get_global_queue(0, 0), ^{
      sleep(10);//网络请求结束后回调是在主线程如果sleep放在外面会阻塞主线程
      NSLog(@"第二个请求完成");
      dispatch_group_leave(dispatchGroup);
    });
  } des:@"第二个url"];
  dispatch_group_notify(dispatchGroup, dispatch_get_main_queue(), ^(){
    NSLog(@"请求完成");
  });
}