Delphi ActiveX

Starting an Asynchronous Task

Chilkat methods that have a name ending in "Async" return a task object. The task object can be run asynchronously on Chilkat's background thread pool. The purpose of this example is to demonstrate how a Task is started via the Run method. It also demonstrates how an application can check on the status of the task, and get the task return value. See the online reference documentation for the full details of the task and task chain objects. Also see the "Task" category on example-code.com for more examples. Delphi ActiveX

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Chilkat_TLB;

...

procedure TForm1.Button1Click(Sender: TObject);
var
success: Integer;
mailman: TChilkatMailMan;
email: TChilkatEmail;
task: IChilkatTask;
curPctDone: Integer;

begin
success := 0;

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

success := 0;

mailman := TChilkatMailMan.Create(Self);

// Set the SMTP server and any required settings.
mailman.SmtpHost := 'smtp.mymailserver.com';
mailman.SmtpUsername := 'myLogin';
mailman.SmtpPassword := 'myPassword';
mailman.StartTLS := 1;

// Create a new email object
email := TChilkatEmail.Create(Self);

email.Subject := 'This is a test';
email.Body := 'This is a test';
email.From := 'Chilkat Support <support@chilkatsoft.com>';
success := email.AddTo('Chilkat Admin','admin@chilkatsoft.com');

// Call the async version of the SendEmail method to return a task object.
// The task object is loaded, but is in the Inert state -- meaning it is
// not yet scheduled to run on Chilkat's background thread pool.
task := mailman.SendEmailAsync(email.ControlInterface);
if (mailman.LastMethodSuccess = 0) then
  begin
    Memo1.Lines.Add(mailman.LastErrorText);
    Exit;
  end;

// Schedule the task for running on the thread pool.  This changes the task's state
// from Inert to Live.
success := task.Run();
if (success <> 1) then
  begin
    Memo1.Lines.Add(task.LastErrorText);

    Exit;
  end;

// The application is now free to do anything else
// while the email is being sent.

// For this example, we'll simply sleep and periodically
// check to see if the SendEmail if finished.  While checking
// however, we'll report on the progress.
curPctDone := 0;
while task.Finished <> 1 do
  begin

    if (task.PercentDone <> curPctDone) then
      begin
        curPctDone := task.PercentDone;
        Memo1.Lines.Add(IntToStr(curPctDone) + ' percent done');
      end;

    // Sleep 100 ms.
    task.SleepMs(100);

  end;

// A finished task could be one that was canceled, aborted, or truly finished.  

// If the task was "canceled", it was canceled prior to actually starting.  This could
// happen if the task was canceled while waiting in a thread pool queue to be scheduled by Chilkat's
// background thread pool scheduler.  

// If the task was "aborted", it indicates that it was canceled while running in a background thread.  
// The ResultErrorText will likely indicate that the task was aborted.

// If the task "completed", then it ran to completion, but the actual success/failure of the method
// is determined by the result obtained via a GetResult* method.  (A "completed" task will
// have a StatusInt equal to 7.   If the task finished, but was not completed, then it must've
// been aborted or canceled:
if (task.StatusInt <> 7) then
  begin
    Memo1.Lines.Add('Task did not complete.');
    Memo1.Lines.Add('task status: ' + task.Status);

    Exit;
  end;

// The SendEmail method returns a boolean.  Therefore, after the task is finished,
// we can get the boolean result by calling GetResultBool.  This is the return value had
// we called SendEmail synchronously.
success := task.GetResultBool();
if (success <> 1) then
  begin
    // The task's ResultErrorText contains what would have been in the LastErrorText property had
    // the SendEmail method been called synchronously.
    Memo1.Lines.Add(task.ResultErrorText);
  end
else
  begin
    Memo1.Lines.Add('Email sent asynchronously.');
  end;

success := mailman.CloseSmtpConnection();
if (success <> 1) then
  begin
    Memo1.Lines.Add('Connection to SMTP server not closed cleanly.');

  end;
end;