Delphi DLL

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 DLL

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

...

procedure TForm1.Button1Click(Sender: TObject);
var
success: Boolean;
mailman: HCkMailMan;
task: HCkTask;
maxWaitMs: Integer;
numMessages: Integer;
email: HCkEmail;
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 := CkMailMan_Create();

// Set the POP3 server's hostname
CkMailMan_putMailHost(mailman,'pop.example.com');

// Set the POP3 login/password and any other requirements..
CkMailMan_putPopUsername(mailman,'myLogin');
CkMailMan_putPopPassword(mailman,'myPassword');
CkMailMan_putPopSsl(mailman,True);
CkMailMan_putMailPort(mailman,995);

// Connect to the POP3 server:
task := CkMailMan_Pop3BeginSessionAsync(mailman);
if (CkMailMan_getLastMethodSuccess(mailman) = False) then
  begin
    Memo1.Lines.Add(CkMailMan__lastErrorText(mailman));
    Exit;
  end;

// Start the background task.
success := CkTask_Run(task);
if (not success) then
  begin
    Memo1.Lines.Add(CkTask__lastErrorText(task));
    CkTask_Dispose(task);
    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 := CkTask_Wait(task,maxWaitMs);
if (not success or (CkTask_getStatusInt(task) <> 7) or (CkTask_getTaskSuccess(task) <> True)) then
  begin
    if (not success) then
      begin
        // The task.LastErrorText applies to the Wait method call.
        Memo1.Lines.Add(CkTask__lastErrorText(task));
      end
    else
      begin
        // The ResultErrorText applies to the underlying task method call (i.e. the Pop3BeginSession)
        Memo1.Lines.Add(CkTask__status(task));
        Memo1.Lines.Add(CkTask__resultErrorText(task));
      end;
    CkTask_Dispose(task);
    Exit;
  end;

CkTask_Dispose(task);

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

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

success := CkTask_Run(task);
success := CkTask_Wait(task,maxWaitMs);
numMessages := CkTask_GetResultInt(task);
CkTask_Dispose(task);
if (numMessages = 0) then
  begin
    Exit;
  end;

email := CkEmail_Create();

for i := 1 to numMessages do
  begin

    task := CkMailMan_FetchByMsgnumAsync(mailman,i);
    if (CkMailMan_getLastMethodSuccess(mailman) = False) then
      begin
        Memo1.Lines.Add(CkMailMan__lastErrorText(mailman));
        Exit;
      end;

    success := CkTask_Run(task);
    success := CkTask_Wait(task,maxWaitMs);
    if (not success or (CkTask_getStatusInt(task) <> 7) or (CkTask_getTaskSuccess(task) <> True)) then
      begin
        if (not success) then
          begin
            // The task.LastErrorText applies to the Wait method call.
            Memo1.Lines.Add(CkTask__lastErrorText(task));
          end
        else
          begin
            // The ResultErrorText applies to the underlying task method call (i.e. the FetchByMsgnum)
            Memo1.Lines.Add(CkTask__status(task));
            Memo1.Lines.Add(CkTask__resultErrorText(task));
          end;
        CkTask_Dispose(task);
        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 := CkEmail_LoadTaskResult(email,task);
    CkTask_Dispose(task);

    if (not success) then
      begin
        Memo1.Lines.Add(CkEmail__lastErrorText(email));
        Exit;
      end
    else
      begin
        Memo1.Lines.Add(CkEmail__from(email) + ': ' + CkEmail__subject(email) + #10);
      end;

  end;

CkMailMan_Dispose(mailman);
CkEmail_Dispose(email);

end;