Pascal (Lazarus/Delphi)

Get the Index of a JSON Member

See more JSON Examples

This example demonstrates how to get the index of a given member by name.

{
  "name": "donut",
  "image":
    {
    "fname": "donut.jpg",
    "w": 200,
    "h": 200
    },
  "thumbnail":
    {
    "fname": "donutThumb.jpg",
    "w": 32,
    "h": 32
    }
}

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.JsonObject;

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

procedure RunDemo;
var
  success: Boolean;
  json: TJsonObject;
  jsonStr: string;
  nameIndex: Integer;
  thumbIndex: Integer;
  fnameIndex: Integer;
  imageObj: TJsonObject;

begin
  success := False;

  json := TJsonObject.Create;

  //  This is the above JSON with whitespace chars removed (SPACE, TAB, CR, and LF chars).
  //  The presence of whitespace chars for pretty-printing makes no difference to the Load
  //  method. 
  jsonStr := '{"name": "donut","image":{"fname": "donut.jpg","w": 200,"h": 200},"thumbnail":{"fname": "donutThumb.jpg","w": 32,"h": 32}}';

  success := json.Load(jsonStr);
  if (success = False) then
    begin
      WriteLn(json.LastErrorText);
      Exit;
    end;

  //  The top-level JSON object has three members: name, image, and thumbnail.
  nameIndex := json.IndexOf('name');
  //  The index of the "name" member is 0.
  WriteLn('nameIndex = ' + nameIndex);

  thumbIndex := json.IndexOf('thumbnail');
  //  The index of the "thumbnail" member is 2.
  WriteLn('thumbIndex = ' + thumbIndex);

  //  The "fname" member is NOT a direct member of the top-level JSON object.
  //  It is a member of a nested object.  If we try to get the index of this
  //  member using the top-level JSON object, it is not found (and returns -1).
  fnameIndex := json.IndexOf('fname');
  //  The fnameIndex is -1 (not found).  This is correct.
  WriteLn('fnameIndex = ' + fnameIndex);

  //  Get the "image" object.
  imageObj := TJsonObject.Create;
  json.ObjectOf2('image',imageObj);

  //  Now we can get the index of the "fname" object, because it is a direct
  //  member of the "image" object:
  fnameIndex := imageObj.IndexOf('fname');
  WriteLn('fnameIndex = ' + fnameIndex);


  json.Free;
  imageObj.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.