Delphi ActiveX

Async Task Chain (another example)

See more Async Examples

Demonstrates using a task chain to run a sequence of FTP tasks asynchronously. 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;
ftp: TChilkatFtp2;
taskChain: TChilkatTaskChain;
task: IChilkatTask;
localFilename: WideString;
remoteFilename: WideString;
numTasks: Integer;
taskIdx: Integer;

begin
success := 0;

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

success := 0;

ftp := TChilkatFtp2.Create(Self);

ftp.Hostname := 'ftp.example.com';
ftp.Username := 'login';
ftp.Password := 'password';

// Connect and login to the FTP server.
success := ftp.Connect();
if (success <> 1) then
  begin
    Memo1.Lines.Add(ftp.LastErrorText);
    Exit;
  end;

taskChain := TChilkatTaskChain.Create(Self);

// Create a task to change to the remote directory where the file will be uploaded.
task := ftp.ChangeRemoteDirAsync('junk');
if (ftp.LastMethodSuccess = 0) then
  begin
    Memo1.Lines.Add(ftp.LastErrorText);
    Exit;
  end;
// Add this task to the task chain.
success := taskChain.Append(task);

// Create a task to upload a file.
localFilename := 'c:/temp/hamlet.xml';
remoteFilename := 'hamlet.xml';

task := ftp.PutFileAsync(localFilename,remoteFilename);
if (ftp.LastMethodSuccess = 0) then
  begin
    Memo1.Lines.Add(ftp.LastErrorText);
    Exit;
  end;

// Add this task to the task chain.
success := taskChain.Append(task);

// Start the task chain running in a background thread.
// Each task is run one after the other (on the same background thread) until all tasks have completed.
// The task chain will stop at the first task that fails.
taskChain.StopOnFailedTask := 1;
success := taskChain.Run();
if (not success) then
  begin
    Memo1.Lines.Add(taskChain.LastErrorText);
    Exit;
  end;

// The application is now free to do anything else
// while the FTP commands are being run...

// For this example, we'll simply sleep and periodically
// check to see if the taskchain if finished. 
while taskChain.Finished <> 1 do
  begin

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

  end;

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

// If the task chain "completed", then it ran to completion.  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 (taskChain.StatusInt <> 7) then
  begin
    Memo1.Lines.Add('Task did not complete.');
    Memo1.Lines.Add('task chain status: ' + taskChain.Status);
    Exit;
  end;

// If we got to this point, the ChangeRemoteDir and PutFile were successful.
// We can visually verify by examining the LastErrorText that was recorded for each
// of these method calls..
numTasks := taskChain.NumTasks;
taskIdx := 0;

while (taskIdx < numTasks) do
  begin

    task := taskChain.GetTask(taskIdx);

    // Examine the status of this task, and the ResultErrorText
    // (the ResultErrorText is the ftp.LastErrorText captured for FTP method called by the task).
    // Everything should indicate success.
    Memo1.Lines.Add('task status: ' + task.Status);
    Memo1.Lines.Add('task log: ' + task.ResultErrorText);

    taskIdx := taskIdx + 1;
  end;

success := ftp.Disconnect();
end;