Delphi DLL

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
    }
}

Delphi DLL

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, JsonObject;

...

procedure TForm1.Button1Click(Sender: TObject);
var
success: Boolean;
json: HCkJsonObject;
jsonStr: PWideChar;
nameIndex: Integer;
thumbIndex: Integer;
fnameIndex: Integer;
imageObj: HCkJsonObject;

begin
success := False;

json := CkJsonObject_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 := CkJsonObject_Load(json,jsonStr);
if (success = False) then
  begin
    Memo1.Lines.Add(CkJsonObject__lastErrorText(json));
    Exit;
  end;

// The top-level JSON object has three members: name, image, and thumbnail.
nameIndex := CkJsonObject_IndexOf(json,'name');
// The index of the "name" member is 0.
Memo1.Lines.Add('nameIndex = ' + IntToStr(nameIndex));

thumbIndex := CkJsonObject_IndexOf(json,'thumbnail');
// The index of the "thumbnail" member is 2.
Memo1.Lines.Add('thumbIndex = ' + IntToStr(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 := CkJsonObject_IndexOf(json,'fname');
// The fnameIndex is -1 (not found).  This is correct.
Memo1.Lines.Add('fnameIndex = ' + IntToStr(fnameIndex));

// Get the "image" object.
imageObj := CkJsonObject_Create();
CkJsonObject_ObjectOf2(json,'image',imageObj);

// Now we can get the index of the "fname" object, because it is a direct
// member of the "image" object:
fnameIndex := CkJsonObject_IndexOf(imageObj,'fname');
Memo1.Lines.Add('fnameIndex = ' + IntToStr(fnameIndex));

CkJsonObject_Dispose(json);
CkJsonObject_Dispose(imageObj);

end;