Dart

JSON Paths

See more JSON Examples

Demonstrates using "Chilkat JSON Paths" to access parts of a JSON document, or to iterate over parts.

This example uses the following JSON document:

{
    "nestedArray" : [
			[
				[1,2,3],
				[4,5,6],
				[7,8,9,10]
			],
			[
				[11,12,13],
				[14,15,16],
				[17,18,19,20]
			],
			[
				[21,22,23],
				[24,25,26],
				[27,28,29,30],
				[31,32,33,34,35,36]
			]
		],

	"nestedObject" : {
		"aaa" : {
			"bb1" : {
				"cc1" : "c1Value",
				"cc2" : "c2Value",
				"cc3" : "c3Value"
			},
			"bb2" : {
				"dd1" : "d1Value",
				"dd2" : "d2Value",
				"dd3" : "d3Value"
			}
		}
	},

	"mixture" : {
		"arrayA" : [  
			{ "fruit": "apple", "animal": "horse", "job": "fireman", "colors": ["red","blue","green"] },
			{ "fruit": "pear", "animal": "plankton", "job": "waiter", "colors": ["yellow","orange","purple"] },
			{ "fruit": "kiwi", "animal": "echidna", "job": "astronaut", "colors": ["magenta","tan","pink"] }
			]
	},


        "name.with.dots" : { "grain" : "oats" }

	
}

Dart

import 'package:chilkat/chilkat.dart';

void main() {
  final json = CkJsonObject();
  json.emitCompact = false;

  // Assume the file contains the data as shown above..
  try {
    json.loadFile('qa_data/json/pathSample.json');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // First, let's get the value of "cc1"
  // The path to this value is: nestedObject.aaa.bb1.cc1
  print(json.stringOf('nestedObject.aaa.bb1.cc1'));

  // Now let's get number 18 from the nestedArray.
  // It is located at nestedArray[1][2][1]
  // (remember: Indexing is 0-based)
  print('This should be 18: ${json.intOf('nestedArray[1][2][1]')}');

  // We can do the same thing in a more roundabout way using the 
  // I, J, and K properties.  (The I,J,K properties will be convenient
  // for iterating over arrays, as we'll see later.)
  json.i = 1;
  json.j = 2;
  json.k = 1;
  print('This should be 18: ${json.intOf('nestedArray[i][j][k]')}');

  // Let's iterate over the array containing the numbers 17, 18, 19, 20.
  // First, use the SizeOfArray method to get the array size:
  final sz = json.sizeOfArray('nestedArray[1][2]');
  // The size should be 4.
  print('size of array = $sz (should equal 4)');

  // Now iterate...
  for (var i = 0; i < sz; i++) {
    json.i = i;
    print(json.intOf('nestedArray[1][2][i]'));
  }

  // Let's use a triple-nested loop to iterate over the nestedArray:

  // szI should equal 1.
  final szI = json.sizeOfArray('nestedArray');
  for (var i = 0; i < szI; i++) {
    json.i = i;

    final szJ = json.sizeOfArray('nestedArray[i]');
    for (var j = 0; j < szJ; j++) {
      json.j = j;

      final szK = json.sizeOfArray('nestedArray[i][j]');
      for (var k = 0; k < szK; k++) {
        json.k = k;

        print(json.intOf('nestedArray[i][j][k]'));
      }
    }
  }

  // Now let's examine how to navigate to JSON objects contained within JSON arrays.
  // This line of code gets the value "kiwi" contained within "mixture"
  print(json.stringOf('mixture.arrayA[2].fruit'));

  // This line of code gets the color "yellow"
  print(json.stringOf('mixture.arrayA[1].colors[0]'));

  // Getting an object at a path:
  // This gets the 2nd object in "arrayA"

  final obj2 = CkJsonObject();
  json.objectOf2('mixture.arrayA[1]', obj2);

  // This object's "animal" should be "plankton"
  print(obj2.stringOf('animal'));

  // Note that paths are relative to the object, not the absolute root of the JSON document.
  // Starting from obj2, "purple" is at "colors[2]"
  print(obj2.stringOf('colors[2]'));

  // Getting an array at a path:
  // This gets the array containing the colors red, green, blue:

  final arr1 = CkJsonArray();
  json.arrayOf2('mixture.arrayA[0].colors', arr1);

  final szArr1 = arr1.size;
  for (var i = 0; i < szArr1; i++) {
    print('$i: ${arr1.stringAt(i)}');
  }

  // The Chilkat JSON path uses ".", "[", and "]" chars for separators.  When a name
  // contains one of these chars, use double-quotes in the path:
  print(json.stringOf('"name.with.dots".grain'));
}