解雇View Controller不会停止异步任务 [英] Dismissing View Controller not stopping Async Task

问题描述

我正在使用以下代码从新启动的视图控制器中执行一些复杂的后台操作

I'm using the following code to do some complex background operations from a newly launched view controller

 let globalQueue = DispatchQueue.global()
  globalQueue.async {
   //complex job 
  }

当用户单击取消"按钮时，我会致电

When the user clicks on the cancel button, I call

self.dismissViewController(self)

但这似乎并不能停止后台任务.

But it seems this does not stop the background task.

我该如何解决这个问题?

How can I solve this problem?

推荐答案

没有API可以取消正在运行的线程.相反，可以添加取消标志来签入处理响应.

There is no API that can cancel running thread. Instead, can add cancellation flag to check in handling response.

var dispatchItem:DispatchWorkItem!

      func executeDispatch()   {

        dispatchItem = DispatchWorkItem {
          for i in 1...200 {
            sleep(1)
            if !(self.dispatchItem.isCancelled)  {
               print("item \(i)")
            }else {
              print("cancel")
          }
        }

        DispatchQueue.global().async(execute: dispatchItem)
      }


      func stop(_ sender: Any) {

        DispatchQueue.global().async {
          self.dispatchItem.cancel()
        }
      }

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