[Lazarus] Application.QueueAsyncCall and checking if object still exists

[Krzysztof]

Details. This is only draft:

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

TMyObject = class
private
  FHttpThread: TMyThread;
  procedure ProgressProc(Data: PtrInt);
end;

TProgressObj = class
  Status: String;
  Id: Integer;
end;

procedure TMyThread.Execute;
var
  i: Integer;
  prg: TProgressObj;
begin
  for i:=1 to 10 do
  begin
    prg := TProgressObj.Create;
    prg.Status := 'Step ' + inttostr(i);
    prg.Id := i;
    Application.QueueAsyncCall(MyObj.ProgressProc, prg);
  end;
end;

procedure TMyObject.ProgressProc(Data: PtrInt);
var
  prg: TProgressObj;
begin
  Memo1.Append(prg.Status);
  prg.Free;
end;

So, when MyObj is destroyed, Queue list have nonexistent pointer to
ProgressProc
and I must clear it because I created object and don't want memory leaks.
Main problem is: I don't know how to tell thread (which is locked in
QueueAsyncCall critical section), that method pointer which he trying to
post, doesn't exists anymore.

2011/9/22 Michael Schnell <mschnell at lumino.de>

> On 09/22/2011 02:56 PM, Michael Schnell wrote:
>
>>
>>
>> IMHO the better way is to check if the object exists in the main thread
>> when called.
>>
> Obviously you need to use a procedure of some other object (e.g. the thread
> itself) and (if necessary) provide the object i9n question (that might be
> destroyed and NILled) as a parameter.
>
> (BTW if the user programmer does not care for it there is no way to detect
> if an object is destroyed. It would need to be NILled by same.So a library
> function can't check this.)
>
>
> -Michael
>
> --
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