Pascal (Lazarus/Delphi)

Async Methods Returning an String

See more Async Examples

Demonstrates how to call an asynchronous method that returns a string. This example sends an HTTPS GET request to a URL and gets the HTML response. Pascal (Lazarus/Delphi)

program ChilkatDemo;

// Demonstrates using the Chilkat Pascal wrapper via the C bridge DLL.
// Builds as a console application under Lazarus (FPC) or Delphi.

{$IFDEF FPC}
  {$MODE DELPHI}
{$ENDIF}
{$APPTYPE CONSOLE}

uses
  {$IFDEF UNIX}
  cthreads,
  {$ENDIF}
  SysUtils,
  CkDllLoader,
  Chilkat.Task,
  Chilkat.Http;

// ---------------------------------------------------------------------------

procedure RunDemo;
var
  success: Boolean;
  http: THttp;
  task: TTask;
  html: string;

begin
  success := False;

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

  http := THttp.Create;

  task := http.QuickGetStrAsync('https://www.chilkatsoft.com/helloWorld.html');
  if (http.LastMethodSuccess = False) then
    begin
      WriteLn(http.LastErrorText);
      Exit;
    end;
  //  Start the background task.
  success := task.Run();
  if (not success) then
    begin
      WriteLn(task.LastErrorText);
      task.Free;
      Exit;
    end;

  //  The application is now free to do anything else

  //  For this example, we'll simply sleep and periodically
  //  check to see if the HTTPS GET if finished.
  while task.Finished <> True do
    begin
      //  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
      WriteLn('Task did not complete.');
      WriteLn('task status: ' + task.Status);
      task.Free;
      Exit;
    end;

  //  The QuickGetStr method returns a string.  Therefore, after the task is finished,
  //  we can get the string result by calling GetResultString.  This is the return value had
  //  we called QuickGetStr synchronously.
  html := task.GetResultString();

  WriteLn(html);

  task.Free;


  http.Free;

end;

// ---------------------------------------------------------------------------

begin

  try
    RunDemo;
  except
    on E: Exception do
      WriteLn('Unhandled exception: ', E.ClassName, ': ', E.Message);
  end;

  WriteLn;
  {$IFDEF MSWINDOWS}
  WriteLn('Press Enter to exit...');
  ReadLn;
  {$ENDIF}
end.