情况是这样的，每次请求总是时好时坏，要么成功，要么就报这个方法里面的错误

-(void) reachabilityChanged:(NSNotification*) notification
{
  if([self.reachability currentReachabilityStatus] == ReachableViaWiFi)
  {
    DLog(@"Server [%@] is reachable via Wifi", self.hostName);
    [_sharedNetworkQueue setMaxConcurrentOperationCount:6];

    [self checkAndRestoreFrozenOperations];
  }
  else if([self.reachability currentReachabilityStatus] == ReachableViaWWAN)
  {
    if(self.wifiOnlyMode) {

      DLog(@" Disabling engine as server [%@] is reachable only via cellular data.", self.hostName);
      [_sharedNetworkQueue setMaxConcurrentOperationCount:0];
    } else {
      DLog(@"Server [%@] is reachable only via cellular data", self.hostName);
      [_sharedNetworkQueue setMaxConcurrentOperationCount:2];
      [self checkAndRestoreFrozenOperations];
    }
  }
  else if([self.reachability currentReachabilityStatus] == NotReachable)
  {
    DLog(@"Server [%@] is not reachable", self.hostName);
    [self freezeOperations];
  }

  if(self.reachabilityChangedHandler) {
    self.reachabilityChangedHandler([self.reachability currentReachabilityStatus]);
  }
}

请教 @sycx 老师之前用MKNetworkKit的时候碰到过这种奇怪的问题吗？