(Delphi ActiveX) Async TaskCompleted Callback

Demonstrates the use of the TaskCompleted callback for async method calls (i.e. for Chilkat asynchronous methods where the method name ends with "Async").

NOTE: This is very important: The TaskCompleted callback runs in the background thread. (All callbacks from an async task, such as AbortCheck, PercentDone, ProgressInfo, etc. are in the background thread.) An application that uses TaskCompleted must be very careful. For example, user interface elements (such as labels, text boxes, etc.) may not be directly accessible from a background thread, and could crash the application if directly accessed. Also, attempting to debug code running in a background thread from an IDE is likely to crash the IDE.

Chilkat for Delphi Downloads Chilkat ActiveX DLL for Delphi Chilkat non-ActiveX DLL for Delphi * The examples here use the ActiveX DLL.

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.httpTaskCompleted(ASender: TObject;  const completedTask: IChilkatTask);
var
      resp: TChilkatHttpResponse;
success: Integer;
xmlResponse: TChilkatXml;
begin
    // TThread.Synchronize provides safety for callbacks that occur in a background thread..
    TThread.Synchronize(nil, procedure begin
      // 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 (completedTask.StatusInt <> 7) then
        begin
          Memo1.Lines.Add('Task did not complete.');
          Memo1.Lines.Add('task status: ' + completedTask.Status);
          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 := TChilkatHttpResponse.Create(Self);

      success := resp.LoadTaskResult(completedTask.ControlInterface);
      if (success <> 1) then
        begin
          Memo1.Lines.Add(resp.LastErrorText);
          Exit;
        end;

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

      Memo1.Lines.Add('status code: ' + IntToStr(resp.StatusCode));
      Memo1.Lines.Add('response header: ' + resp.Header);

      xmlResponse := TChilkatXml.Create(Self);
      xmlResponse.LoadXml(resp.BodyStr);
      Memo1.Lines.Add(xmlResponse.GetXml());
      end);
end;


procedure TForm1.Button1Click(Sender: TObject);
var
http: TChilkatHttp;
success: Integer;
soapXml: TChilkatXml;
req: TChilkatHttpRequest;
task: IChilkatTask;

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

    http := TChilkatHttp.Create(Self);
    http.OnTaskCompleted := httpTaskCompleted;

    soapXml := TChilkatXml.Create(Self);

    soapXml.Tag := 'soap12:Envelope';
    success := soapXml.AddAttribute('xmlns:xsi','http://www.w3.org/2001/XMLSchema-instance');
    success := soapXml.AddAttribute('xmlns:xsd','http://www.w3.org/2001/XMLSchema');
    success := soapXml.AddAttribute('xmlns:soap12','http://www.w3.org/2003/05/soap-envelope');

    soapXml.NewChild2('soap12:Body','');
    success := soapXml.GetChild2(0);
    soapXml.NewChild2('GetCityWeatherByZIP','');
    success := soapXml.GetChild2(0);
    success := soapXml.AddAttribute('xmlns','http://ws.cdyne.com/WeatherWS/');
    soapXml.NewChild2('ZIP','60187');
    soapXml.GetRoot2();

    Memo1.Lines.Add(soapXml.GetXml());

    req := TChilkatHttpRequest.Create(Self);
    req.HttpVerb := 'POST';
    req.SendCharset := 0;
    req.AddHeader('Content-Type','application/soap+xml; charset=utf-8');
    req.AddHeader('SOAPAction','http://ws.cdyne.com/WeatherWS/GetCityWeatherByZIP');
    req.Path := '/WeatherWS/Weather.asmx';
    success := req.LoadBodyFromString(soapXml.GetXml(),'utf-8');

    http.FollowRedirects := 1;

    // The name of "SynchronousRequestAsync" method is somewhat confusing. This is explained here:

    // Any Chilkat method that utilizes callbacks will have an Async version of the method.
    // The name of the Async method is the method name appended with "Async".  For example,
    // if the method is named "Abc", then the async method is "AbcAsync".
    // The Async method always returns a Chilkat Task object.

    // In the years prior to Chilkat introducing the Async functionality, this particular method's
    // name was already "SynchronousRequest".  The async versionof the method is therefore
    // "SynchronousRequestAsync" (just like "Abc" --> "AbcAsync").  Yes, it's confusing and we apologize.. 
    task := http.SynchronousRequestAsync('wsf.cdyne.com',80,0,req.ControlInterface);
    if (http.LastMethodSuccess <> 1) then
      begin
        Memo1.Lines.Add(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 <> 1) then
      begin
        Memo1.Lines.Add(task.LastErrorText);

        Exit;
      end;

    // The application is now free to do anything else
    // while the HTTP request is in progress.  When the task
    // is completed, the TaskCompleted method is called.

    // -------------------------------------------------------------------------------
    // The following is a general note that applies to all programming languages:
    // -------------------------------------------------------------------------------

    // NOTE: This is very important:  The TaskCompleted callback runs in the background thread.  
    // (All callbacks from an async task, such as AbortCheck, PercentDone, ProgressInfo, etc. are in the background thread.) 
    // An application that uses TaskCompleted must be very careful.  
    // For example, user interface elements (such as labels, text boxes, etc.) may not be directly
    // accessible from a background thread, and could crash the application if directly accessed.  Also, attempting to debug
    // code running in a background thread from an IDE, especially an older IDE (such as VB6) is likely to crash the IDE.
end;