Ios 崩溃：NSOperationQueue 0x170033420:：NSOperation 0x17405fe00（QOS:默认）

我在基于Swift 3.0的iOS应用程序中有一个函数，它应该发送HTTP请求，并在服务器返回值后通过完成块处理它们。然而，我无法在内部重现这种崩溃，但在用户中，我看到它不断发生。代码中的行号在下面的代码段中标记为崩溃。有什么调试建议或线索吗

func sendRequest(_ parameters : NSDictionary?, requestType : String, urlString : String, completionHandler : @escaping (_ succeeded : Bool, _ response : [String : AnyObject]?) -> ()) {
DispatchQueue.global(qos: .background).async {
  let request = NSMutableURLRequest(url: URL(string: urlString)!)
  request.httpMethod = requestType
  request.addValue("application/json", forHTTPHeaderField: "Content-Type")
  request.addValue("application/json", forHTTPHeaderField: "Accept")
  if let jsonParams = parameters {
    do {
      request.httpBody = try JSONSerialization.data(withJSONObject: jsonParams, options: .prettyPrinted)
    } catch {
      self.log.error("Error -> \(error).")
      completionHandler(false, nil)
    }
  }

  let task = URLSession.shared.dataTask(with: request as URLRequest, completionHandler: { data, response, error in
    if error != nil {
      self.log.error("Error -> \(error?.localizedDescription)")
      completionHandler(false, nil)
    }

    do {
      //  -----> Crashes here - not sure why?
      let result = try JSONSerialization.jsonObject(with: data!, options: .mutableLeaves) as? [String : AnyObject]
      completionHandler(true, result)
    } catch {
      self.log.error("Error -> \(error).")
      completionHandler(false, nil)
    }
  })
  task.resume()
}

}

崩溃线程的堆栈跟踪：

Crashed: NSOperationQueue 0x170033420 :: NSOperation 0x17405fe00 (QOS: DEFAULT)
0  Jarvis                         0x1000a6d74 specialized ContextServer.(sendRequest(NSDictionary?, requestType : String, urlString : String, completionHandler : (Bool, [String : AnyObject]?) -> ()) -> ()).(closure #1).(closure #1) (ContextServer.swift:39)
1  Jarvis                         0x1000a5e88 ContextServer.(sendRequest(NSDictionary?, requestType : String, urlString : String, completionHandler : (Bool, [String : AnyObject]?) -> ()) -> ()).(closure #1).(closure #1) (ContextServer.swift)
2  CFNetwork                      0x19063e618 __75-[__NSURLSessionLocal taskForClass:request:uploadFile:bodyData:completion:]_block_invoke + 32
3  CFNetwork                      0x190655318 __49-[__NSCFLocalSessionTask _task_onqueue_didFinish]_block_invoke + 296
4  Foundation                     0x190b017e4 __NSBLOCKOPERATION_IS_CALLING_OUT_TO_A_BLOCK__ + 16
5  Foundation                     0x190a46358 -[NSBlockOperation main] + 96
6  Foundation                     0x190a36954 -[__NSOperationInternal _start:] + 620
7  Foundation                     0x190b03b90 __NSOQSchedule_f + 228
8  libdispatch.dylib              0x18eec91c0 _dispatch_client_callout + 16
9  libdispatch.dylib              0x18eed7444 _dispatch_queue_serial_drain + 928
10 libdispatch.dylib              0x18eecc9a8 _dispatch_queue_invoke + 652
11 libdispatch.dylib              0x18eed938c _dispatch_root_queue_drain + 572
12 libdispatch.dylib              0x18eed90ec _dispatch_worker_thread3 + 124
13 libsystem_pthread.dylib        0x18f0d12c8 _pthread_wqthread + 1288
14 libsystem_pthread.dylib        0x18f0d0db4 start_wqthread + 4

---

崩溃线程的堆栈跟踪是什么样子的？刚刚添加了崩溃线程的堆栈跟踪。我立即怀疑

数据在JSONSerialization行中。您如何保证它不是
nil
？我的第一个猜测是，在某些情况下，您将获得一个成功的HTTP响应代码，其中包含
nil
数据。好的观点->愚蠢的我。我会小心的。我在代码的其他地方做了，但忘了在那里做。@inc_london你是如何防范的。我也在面对它。我已经查过了。如果（data！=nil）{}这行吗？