Pascal (Lazarus/Delphi)

Async Methods Returning an Object

See more Async Examples

Demonstrates how to call an asynchronous method that returns an object. This example reads email from a POP3 server using the Async versions of the Chilkat methods. Pascal (Lazarus/Delphi)

program ChilkatDemo;

// Demonstrates using the Chilkat Pascal wrapper via the C bridge DLL.
// Builds as a console application under Lazarus (FPC) or Delphi.

{$IFDEF FPC}
  {$MODE DELPHI}
{$ENDIF}
{$APPTYPE CONSOLE}

uses
  {$IFDEF UNIX}
  cthreads,
  {$ENDIF}
  SysUtils,
  CkDllLoader,
  Chilkat.MailMan,
  Chilkat.Task,
  Chilkat.Email;

// ---------------------------------------------------------------------------

procedure RunDemo;
var
  success: Boolean;
  mailman: TMailMan;
  task: TTask;
  maxWaitMs: Integer;
  numMessages: Integer;
  email: TEmail;
  i: Integer;

begin
  success := False;

  //  This example assumes the Chilkat API to have been previously unlocked.
  //  See Global Unlock Sample for sample code.

  success := False;

  mailman := TMailMan.Create;

  //  Set the POP3 server's hostname
  mailman.MailHost := 'pop.example.com';

  //  Set the POP3 login/password and any other requirements..
  mailman.PopUsername := 'myLogin';
  mailman.PopPassword := 'myPassword';
  mailman.PopSsl := True;
  mailman.MailPort := 995;

  //  Connect to the POP3 server:
  task := mailman.Pop3BeginSessionAsync();
  if (mailman.LastMethodSuccess = False) then
    begin
      WriteLn(mailman.LastErrorText);
      Exit;
    end;

  //  Start the background task.
  success := task.Run();
  if (not success) then
    begin
      WriteLn(task.LastErrorText);
      task.Free;
      Exit;
    end;
  //  Wait for the POP3 connect task to finish.
  //  The True/False returned by Wait applies to the Wait method call, not the task.
  maxWaitMs := 30000;
  success := task.Wait(maxWaitMs);
  if (not success or (task.StatusInt <> 7) or (task.TaskSuccess <> True)) then
    begin
      if (not success) then
        begin
          //  The task.LastErrorText applies to the Wait method call.
          WriteLn(task.LastErrorText);
        end
      else
        begin
          //  The ResultErrorText applies to the underlying task method call (i.e. the Pop3BeginSession)
          WriteLn(task.Status);
          WriteLn(task.ResultErrorText);
        end;
      task.Free;
      Exit;
    end;

  task.Free;

  //  Get the number of messages in the mailbox.
  task := mailman.GetMailboxCountAsync();

  //  To keep the example short, we'll skip handling failures.
  //  The failures would be handled in the same way as shown above.

  success := task.Run();
  success := task.Wait(maxWaitMs);
  numMessages := task.GetResultInt();
  task.Free;
  if (numMessages = 0) then
    begin
      Exit;
    end;

  email := TEmail.Create;

  for i := 1 to numMessages do
    begin

      task := mailman.FetchByMsgnumAsync(i);
      if (mailman.LastMethodSuccess = False) then
        begin
          WriteLn(mailman.LastErrorText);
          Exit;
        end;

      success := task.Run();
      success := task.Wait(maxWaitMs);
      if (not success or (task.StatusInt <> 7) or (task.TaskSuccess <> True)) then
        begin
          if (not success) then
            begin
              //  The task.LastErrorText applies to the Wait method call.
              WriteLn(task.LastErrorText);
            end
          else
            begin
              //  The ResultErrorText applies to the underlying task method call (i.e. the FetchByMsgnum)
              WriteLn(task.Status);
              WriteLn(task.ResultErrorText);
            end;
          task.Free;
          Exit;
        end;

      //  Each Chilkat object that can be a return value of an asynchronous task will
      //  have a method named LoadTaskResult.  The object returned in the underlying
      //  asynchronous method call is retrieved by calling LoadTaskResult. 

      //  To say it another way: The application will provide a pre-existing object of
      //  the desired return type (in this case it is an email object).  This object is
      //  loaded by calling LoadTaskResult.  

      success := email.LoadTaskResult(task);
      task.Free;

      if (not success) then
        begin
          WriteLn(email.LastErrorText);
          Exit;
        end
      else
        begin
          WriteLn(email.From + ': ' + email.Subject + #10);
        end;

    end;



  mailman.Free;
  email.Free;

end;

// ---------------------------------------------------------------------------

begin

  try
    RunDemo;
  except
    on E: Exception do
      WriteLn('Unhandled exception: ', E.ClassName, ': ', E.Message);
  end;

  WriteLn;
  {$IFDEF MSWINDOWS}
  WriteLn('Press Enter to exit...');
  ReadLn;
  {$ENDIF}
end.