Dart

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
    }
}

Dart

import 'package:chilkat/chilkat.dart';

void main() {
  final json = CkJsonObject();

  // 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. 
  final jsonStr = '{"name": "donut","image":{"fname": "donut.jpg","w": 200,"h": 200},"thumbnail":{"fname": "donutThumb.jpg","w": 32,"h": 32}}';

  try {
    json.load(jsonStr);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

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

  final thumbIndex = json.indexOf('thumbnail');
  // The index of the "thumbnail" member is 2.
  print('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).
  var fnameIndex = json.indexOf('fname');
  // The fnameIndex is -1 (not found).  This is correct.
  print('fnameIndex = $fnameIndex');

  // Get the "image" object.
  final imageObj = CkJsonObject();
  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');
  print('fnameIndex = $fnameIndex');
}