swift - 等待另一个对象(类)完成任务

Question

这个问题已经有答案了:

Returning data from async call in Swift function (13 个回答)

已关闭 5 年前。

我正在尝试等待从我的连接帮助程序对象加载信息，在我看来，我正在显示它。在我看来，我不确定如何处理这个电话。

它是基于这个问题构建的: Waiting for two different REST/Network calls to complete

class ConnectionAPI
{
func getABStructWrapper() -> ABStructWrapper
{
    ConnectionHandler()
    return self.structWrapper
}

//let loader = from Oauth2/p2_OAuth2 pod to load JSON
//other general func and var’s 
func ConnectionHandler()
{

    let dg = DispatchGroup()

    switch self.RequestType
    {
    case aRequest:
        //if I make a single call here, works fine 
    case bRequest:
        //if I make a single call here, works fine 
    case abRequest:
        //when making requests for both type a and b, can’t get it to work
        dg.enter()

        loader.perform(request: self.userDataRequest)
        { response in
            do
            {
                let json = try response.responseJSON()
                self.structWrapper.aArray = self.loadAArray(dict: json)
            }
            catch let error {
                self.didCancelOrFail(error)
            }

           dg.leave()
        }

        dg.enter()

        loader.perform(request: self.userDataRequest)
        { response in
            do
            {
                let json = try response.responseJSON()
                self.structWrapper.bArray = self.loadBArray(dict: json)                }
            catch let error {
                self.didCancelOrFail(error)
            }

          dg.leave()
        }

       //This works! but want to do this from a view
       //commented out in xcode:
        dg.notify(queue: .main) 
        {

          for x in self.structWrapper.aArray                  
           {
             print(x.displayTime + ":" + x.units)
           }
           for y in self.structWrapper.bArray
           {
            print(y.displayTime + ":" + String(y.someNumber) 
           }
            print(“tasks complete”)
         }

    }

}
}

从我的角度来看:

Func getValues
{

        let dg = DispatchGroup()
        dg.enter()
        self.StructWrapper = ConnectionAPI.getABStructWrapper()
        dg.leave()
        dg.notify(queue: .main) 
       {
            //will print, but requests are not complete, arrays are empty, even though breakpoints hit in loading them.
          for x in self.structWrapper.aArray                  
           {
             print(x.displayTime + ":" + x.units)
           }
           for y in self.structWrapper.bArray
           {
            print(y.displayTime + ":" + String(y.someNumber) 
           }
            print(“tasks complete”)
        }
}

Answer 1

在您的请求类中，您需要完成处理程序

class ConnectionAPI {

   static let shared = ConnectionAPI()

   func ConnectionHandler(completion:@escaping(_ finished:Bool)->void) {

      //
      //

     dg.notify(queue: .main) {

       completion(true)
     }

   }

}

注意您需要处理错误情况并发送

completion(false)

//

您在 View 中不需要任何 DispatchGroup，因为您已经在网络类中完成了它们

func getValues() {
     ConnectionAPI.shared.ConnectionHandler {  (finished) in

       if finished {
          print(ConnectionAPI.shared.aArray)
       }
     }
  }