Delphi ActiveX

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. 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;
task: IChilkatTask;
maxWaitMs: Integer;
numMessages: Integer;
email: TChilkatEmail;
i: 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 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 := 1;
mailman.MailPort := 995;

// Connect to the POP3 server:
task := mailman.Pop3BeginSessionAsync();
if (mailman.LastMethodSuccess = 0) then
  begin
    Memo1.Lines.Add(mailman.LastErrorText);
    Exit;
  end;

// Start the background task.
success := task.Run();
if (not success) then
  begin
    Memo1.Lines.Add(task.LastErrorText);

    Exit;
  end;
// Wait for the POP3 connect task to finish.
// The 1/0 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 <> 1)) then
  begin
    if (not success) then
      begin
        // The task.LastErrorText applies to the Wait method call.
        Memo1.Lines.Add(task.LastErrorText);
      end
    else
      begin
        // The ResultErrorText applies to the underlying task method call (i.e. the Pop3BeginSession)
        Memo1.Lines.Add(task.Status);
        Memo1.Lines.Add(task.ResultErrorText);
      end;

    Exit;
  end;

// 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();

if (numMessages = 0) then
  begin
    Exit;
  end;

email := TChilkatEmail.Create(Self);

for i := 1 to numMessages do
  begin

    task := mailman.FetchByMsgnumAsync(i);
    if (mailman.LastMethodSuccess = 0) then
      begin
        Memo1.Lines.Add(mailman.LastErrorText);
        Exit;
      end;

    success := task.Run();
    success := task.Wait(maxWaitMs);
    if (not success or (task.StatusInt <> 7) or (task.TaskSuccess <> 1)) then
      begin
        if (not success) then
          begin
            // The task.LastErrorText applies to the Wait method call.
            Memo1.Lines.Add(task.LastErrorText);
          end
        else
          begin
            // The ResultErrorText applies to the underlying task method call (i.e. the FetchByMsgnum)
            Memo1.Lines.Add(task.Status);
            Memo1.Lines.Add(task.ResultErrorText);
          end;

        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);

    if (not success) then
      begin
        Memo1.Lines.Add(email.LastErrorText);
        Exit;
      end
    else
      begin
        Memo1.Lines.Add(email.From + ': ' + email.Subject + #10);
      end;

  end;
end;