Lazarus Pascal Requires Chilkat v11.7.0+

Handle QR Code Errors

See more QR Code Examples

Demonstrates what happens when a request is refused. QrCode returns false and the response holds errors[0] with three members: a code that does not change between versions, the path of the request member at fault (a JSON Pointer such as /encoding/qr/version), and a message. Requests are checked strictly, so a misspelled option is an error rather than being silently ignored. LastErrorText has the same information in more detail. Lazarus Pascal

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.Formats,
  Chilkat.JsonObject;

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

procedure RunDemo;
var
  success: Boolean;
  fmt: TFormats;
  json: TJsonObject;
  jsonOut: TJsonObject;

begin
  success := False;

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

  fmt := TFormats.Create;
  json := TJsonObject.Create;
  jsonOut := TJsonObject.Create;

  //  1. A misspelled option: "moduleSise" for "moduleSize".
  json.UpdateString('payload.text','https://www.chilkatsoft.com/');
  json.UpdateInt('render.moduleSise',8);
  success := fmt.QrCode('generate',json,jsonOut);
  if (success = False) then
    begin
      WriteLn('code: ' + jsonOut.StringOf('errors[0].code'));
      WriteLn('path: ' + jsonOut.StringOf('errors[0].path'));
      WriteLn('message: ' + jsonOut.StringOf('errors[0].message'));
    end;

  //  2. A value out of range: QR versions are 1 to 40.
  json.Clear();
  json.UpdateString('payload.text','https://www.chilkatsoft.com/');
  json.UpdateInt('encoding.qr.version',41);
  success := fmt.QrCode('generate',json,jsonOut);
  if (success = False) then
    begin
      WriteLn('code: ' + jsonOut.StringOf('errors[0].code'));
      WriteLn('path: ' + jsonOut.StringOf('errors[0].path'));
      WriteLn('message: ' + jsonOut.StringOf('errors[0].message'));
    end;

  //  3. Too much data: this text does not fit a version 1 symbol.
  json.Clear();
  json.UpdateString('payload.text','https://www.chilkatsoft.com/barcode_overview.asp');
  json.UpdateInt('encoding.qr.version',1);
  success := fmt.QrCode('generate',json,jsonOut);
  if (success = False) then
    begin
      WriteLn('code: ' + jsonOut.StringOf('errors[0].code'));
      WriteLn('path: ' + jsonOut.StringOf('errors[0].path'));
      WriteLn('message: ' + jsonOut.StringOf('errors[0].message'));
    end;

  //  A program can act on the code.
  if (jsonOut.StringOf('errors[0].code') = 'capacityExceeded') then
    begin
      WriteLn('The text is too long for the symbol size allowed.');
    end;

  //  Sample output:

  //  code: unknownOption
  //  path: /render/moduleSise
  //  message: unknown option
  //  code: outOfRange
  //  path: /encoding/qr/version
  //  message: the value is out of range
  //  code: capacityExceeded
  //  path: /payload
  //  message: the payload does not fit the requested QR version at the requested error-correction level
  //  The text is too long for the symbol size allowed.


  fmt.Free;
  json.Free;
  jsonOut.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.