Pascal (Lazarus/Delphi)

Modify Parts of JSON Document

See more JSON Examples

Demonstrates how to modify parts of a JSON document. This example uses the following JSON document:

{
   "fruit": [
      	{
         "kind": "apple",
	 "count": 24,
	 "fresh": true,
	 "extraInfo": null,
	 "listA": [ "abc", 1, null, false ],
	 "objectB": { "animal" : "monkey" }
      	},
	{
         "kind": "pear",
	 "count": 18,
	 "fresh": false,
	 "extraInfo": null
	 "listA": [ "xyz", 24, null, true ],
	 "objectB": { "animal" : "lemur" }
	}
    ],
    "list" : [ "banana", 12, true, null, "orange", 12.5, { "ticker": "AAPL" }, [ 1, 2, 3, 4, 5 ] ],
    "alien" : true
}

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.JsonArray,
  Chilkat.JsonObject;

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

procedure RunDemo;
var
  success: Boolean;
  json: TJsonObject;
  listA: TJsonArray;
  bNull: Boolean;
  tickerObj: TJsonObject;
  aa: TJsonArray;
  aFruit: TJsonArray;
  appleObj: TJsonObject;
  pearObj: TJsonObject;

begin
  success := False;

  json := TJsonObject.Create;

  //  Load the JSON from a file.
  success := json.LoadFile('qa_data/json/modifySample.json');
  if (success = False) then
    begin
      WriteLn(json.LastErrorText);
      Exit;
    end;

  //  This example will not check for errors (i.e. null / false / 0 return values)...

  //  Get the "list" array:

  listA := TJsonArray.Create;

  json.ArrayOf2('list',listA);

  //  Modify values in the list.

  //  Change banana to plantain
  success := listA.SetStringAt(0,'plantain');

  //  Change 12 to 24
  success := listA.SetIntAt(1,24);

  //  Change true to false
  success := listA.SetBoolAt(2,False);

  //  Is the 3rd item null?
  bNull := listA.IsNullAt(3);

  //  Change "orange" to 32.
  success := listA.SetIntAt(4,32);

  //  Change 12.5 to 31.2
  success := listA.SetNumberAt(5,'31.2');

  //  Replace the { "ticker" : "AAPL" } object with { "ticker" : "GOOG" }
  //  Do this by deleting, then inserting a new object at the same location.
  success := listA.DeleteAt(6);
  tickerObj := TJsonObject.Create;
  listA.AddObjectAt2(6,tickerObj);

  success := tickerObj.AppendString('ticker','GOOG');

  //  Replace "[ 1, 2, 3, 4, 5 ]" with "[ "apple", 22, true, null, 1080.25 ]"
  success := listA.DeleteAt(7);
  aa := TJsonArray.Create;
  listA.AddArrayAt2(7,aa);

  success := aa.AddStringAt(-1,'apple');
  success := aa.AddIntAt(-1,22);
  success := aa.AddBoolAt(-1,True);
  success := aa.AddNullAt(-1);
  success := aa.AddNumberAt(-1,'1080.25');

  //  Get the "fruit" array
  aFruit := TJsonArray.Create;
  json.ArrayAt2(0,aFruit);

  //  Get the 1st element:
  appleObj := TJsonObject.Create;
  aFruit.ObjectAt2(0,appleObj);

  //  Modify values by member name:
  success := appleObj.SetStringOf('fruit','fuji_apple');
  success := appleObj.SetIntOf('count',46);
  success := appleObj.SetBoolOf('fresh',False);
  success := appleObj.SetStringOf('extraInfo','developed by growers at the Tohoku Research Station in Fujisaki');

  //  Modify values by index:

  pearObj := TJsonObject.Create;
  aFruit.ObjectAt2(1,pearObj);

  success := pearObj.SetStringAt(0,'bartlett_pear');
  success := pearObj.SetIntAt(1,12);
  success := pearObj.SetBoolAt(2,False);
  success := pearObj.SetStringAt(3,'harvested in late August to early September');

  json.EmitCompact := False;
  WriteLn(json.Emit());


  json.Free;
  listA.Free;
  tickerObj.Free;
  aa.Free;
  aFruit.Free;
  appleObj.Free;
  pearObj.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.