Restart Delphi TThread that lives the entire app lifetime

I have created a class that derives from TThread, because I wish to do some async stuff, however to avoid having to create another class, I built the entire thing around that thread class. Not sure if this is good practice or not, and if I cant get this to work, well then I suppose I have no choice but to recode..

The problem: I create the Thread on FormCreate, assign some properties, and I Free it on FormDestroy. In the Thread's constructor, I set Fr开发者_开发问答eeOnTerminate = False. When I click on a button on my Form, I Start(); the Thread. Okay, so it runs as expected, an error occurs (expected!), its being passed to my error handling event, and it appears to terminate. I then click the button again, and I get a Cannot call Start on a running or suspended thread error.

How can I finish the thread without freeing it, and enabling me to start it again?

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You can't restart a thread once it is finished/terminated. In that case you should just create a new instance if the thread again like you did in FormCreate.

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Catch the error in the thread, handle it there and then let the thread continue the work. To handle the error you could simply queue a method to the main thread to report the error, for example. I hope you aren't letting exceptions leave your thread Execute method.

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This is the way that I implement it:

procedure TAPIRequest.DoRequest;
begin
  FBusy := True;
  Resume;
end;


procedure TAPIRequest.Execute;
begin
  inherited;

  while not Terminated do begin
    HttpError := False;

    try
      Response := HTTP.Post(URL, Params);
      ParseResponse;

    except
      HttpError := True;
    end;

    if Assigned(OnResponse) then
      OnResponse();

    FBusy := False;
    Suspend;
  end;
end;

---

type
  TMyThread = class(TThread)
  protected
    procedure Execute; override;
  end;

var
  Form1: TForm1;
  MyThread: TMyThread;
  Event: TEvent;

procedure TForm1.FormCreate(Sender: TObject);
begin
  Event := TEvent.Create(nil,true,false, '');
  MyThread := TMyThread.Create(False);
end;

procedure TMyThread.Execute;
begin
  while True do
    begin
      Event.WaitFor(Infinite);

      // do something

      Event.ResetEvent;
    end;
end;

procedure RestartThread;
begin
    Event.SetEvent;
// if you need check thread status, wait or run, use here 
// if Event.WaitFor(0) = ...(wrTimeout, wrSignaled)
end;