Delphi DLL

Async Task Chain (another example)

See more Async Examples

Demonstrates using a task chain to run a sequence of FTP tasks asynchronously. Delphi DLL

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Task, Ftp2, TaskChain;

...

procedure TForm1.Button1Click(Sender: TObject);
var
success: Boolean;
ftp: HCkFtp2;
taskChain: HCkTaskChain;
task: HCkTask;
localFilename: PWideChar;
remoteFilename: PWideChar;
numTasks: Integer;
taskIdx: Integer;

begin
success := False;

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

success := False;

ftp := CkFtp2_Create();

CkFtp2_putHostname(ftp,'ftp.example.com');
CkFtp2_putUsername(ftp,'login');
CkFtp2_putPassword(ftp,'password');

// Connect and login to the FTP server.
success := CkFtp2_Connect(ftp);
if (success <> True) then
  begin
    Memo1.Lines.Add(CkFtp2__lastErrorText(ftp));
    Exit;
  end;

taskChain := CkTaskChain_Create();

// Create a task to change to the remote directory where the file will be uploaded.
task := CkFtp2_ChangeRemoteDirAsync(ftp,'junk');
if (CkFtp2_getLastMethodSuccess(ftp) = False) then
  begin
    Memo1.Lines.Add(CkFtp2__lastErrorText(ftp));
    Exit;
  end;
// Add this task to the task chain.
success := CkTaskChain_Append(taskChain,task);
CkTask_Dispose(task);

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

task := CkFtp2_PutFileAsync(ftp,localFilename,remoteFilename);
if (CkFtp2_getLastMethodSuccess(ftp) = False) then
  begin
    Memo1.Lines.Add(CkFtp2__lastErrorText(ftp));
    Exit;
  end;

// Add this task to the task chain.
success := CkTaskChain_Append(taskChain,task);
CkTask_Dispose(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.
CkTaskChain_putStopOnFailedTask(taskChain,True);
success := CkTaskChain_Run(taskChain);
if (not success) then
  begin
    Memo1.Lines.Add(CkTaskChain__lastErrorText(taskChain));
    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 CkTaskChain_getFinished(taskChain) <> True do
  begin

    // Sleep 100 ms.
    CkTaskChain_SleepMs(taskChain,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 (CkTaskChain_getStatusInt(taskChain) <> 7) then
  begin
    Memo1.Lines.Add('Task did not complete.');
    Memo1.Lines.Add('task chain status: ' + CkTaskChain__status(taskChain));
    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 := CkTaskChain_getNumTasks(taskChain);
taskIdx := 0;

while (taskIdx < numTasks) do
  begin

    task := CkTaskChain_GetTask(taskChain,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: ' + CkTask__status(task));
    Memo1.Lines.Add('task log: ' + CkTask__resultErrorText(task));

    CkTask_Dispose(task);

    taskIdx := taskIdx + 1;
  end;

success := CkFtp2_Disconnect(ftp);

CkFtp2_Dispose(ftp);
CkTaskChain_Dispose(taskChain);

end;