Pascal (Lazarus/Delphi)

Getting the HTTP Response after an Asynchronous HTTP Request Completes

See more HTTP Examples

Some HTTP methods return an HTTP response object. This example demonstrates how to obtain the HTTP response object for such a method when calling asynchronously. 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.Http,
  Chilkat.Task,
  Chilkat.HttpResponse;

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

procedure RunDemo;
var
  success: Boolean;
  http: THttp;
  task: TTask;
  resp: THttpResponse;

begin
  success := False;

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

  success := False;

  http := THttp.Create;

  //  Call the async version of the QuickGetObj method to return a task object.
  //  The task object is loaded, but is in the Inert state -- meaning it is
  //  not yet scheduled to run on Chilkat's background thread pool.
  task := http.QuickGetObjAsync('https://stackexchange.com');
  if (http.LastMethodSuccess <> True) then
    begin
      WriteLn(http.LastErrorText);
      Exit;
    end;

  //  Schedule the task for running on the thread pool.  This changes the task's state
  //  from Inert to Live.
  success := task.Run();
  if (success <> True) then
    begin
      WriteLn(task.LastErrorText);
      task.Free;
      Exit;
    end;

  //  The application is now free to do anything else
  //  while the HTML page is being downloaded.

  //  For this example, we'll simply sleep and periodically
  //  check to see if the QuickGetObjAsync 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 synchronous call to QuickGetObj would return an HTTP response object.  To get this 
  //  response object for the async call, we instantiate a new/empty HTTP response object,
  //  and then load it from the completed task.
  resp := THttpResponse.Create;

  success := resp.LoadTaskResult(task);
  if (success <> True) then
    begin
      WriteLn(resp.LastErrorText);
      task.Free;
      Exit;
    end;

  task.Free;

  //  Now that we have the response, we can get all of the information:

  WriteLn('status code: ' + resp.StatusCode);
  WriteLn('response header: ' + resp.Header);

  //  ...


  http.Free;
  resp.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.