ios - 如何在后端作业中实现纺车？

Question

我需要在后端作业中实现一个纺车。我的后端作业在一个单独的类中。

class ViewControllerA: UITableViewController {

  // Code
  var GetBackendRecordObj = GetBackendRecord(initparam:param);

  // CODE TO START ANIMATION (SPINNING WHEEL)  

  self.view.addSubview(self.activityIndicator)
  self.activityIndicator.bringSubview(toFront: self.view)
  self.activityIndicator.startAnimating()

  // CODE TO CALL THE BACKEND IS IN ANOTHER CLASS         
  GetBackendRecordObj.fetch_record()


}



class GetBackendRecord{

  var transaction_id: String = ""
  var current_email_id: String = ""

  init(initparam: String) {
    self.initparam = initparam

  }

func fetch_record (){

    do{
        DispatchQueue.global(qos: .userInitiated).async {
            //code
            DispatchQueue.main.async { () -> Void in
                //code to process response from backend
                // NEED CODE TO STOP ANIMATION (SPINNING WHEEL)THAT WAS STARTED IN VIEWCONTROLLERA
            })
        }
   }
}              

如何在后端调用完成后访问 UITableViewcontroller，以便停止动画。或者如果在执行后端作业(在单独的类中)时有更好的启动/停止动画的方法，请告诉我。

Answer 1

将完成处理程序添加到 fetch_record:

func fetch_record(_ completionHandler: @escaping () -> Swift.Void) {
    do{
        DispatchQueue.global(qos: .userInitiated).async {
            //code
            DispatchQueue.main.async { () -> Void in
                //code to process response from backend
                completionHandler()
            })
        }
   }
}  

在您的 ViewController 中调用它时，您可以指定完成后要执行的操作:

GetBackendRecordObj.fetch_record() {
    self.activityIndicator.stopAnimating()
}