Sort maps in Dart by key or by value

Question

I have the following map

Map testMap = { 
  3 : {
    'order': 3,
    'sample' : 'sample'
  },
  2 : {
    'order': 2,
    'sample' : 'sample'
  },
  1 : {
    'order': 1,
    'sample' : 'sample'
  },
  4: {
    'order': 4,
    'sample' : 'sample'
  }
};

How i can sort it by key, if not possible by the 'order' value inside child map.

Note: the Map grows up to 100 fields.

SOLVED i must have been tired before, but just in case someone else is looking here is my solution. Also, ordering just by key with SplayTreeMap produce a strange order like this 1,10,11,12,13,14,15,16,17,18,19,2,20,21 ...

import 'dart:collection';

void main() {
  Map testMap = {
     11: {
      'order': '11',
      'sample' : 'sample'
    },
    3 : {
      'order': '3',
      'sample' : 'sample'
    },
    2 : {
      'order': '2',
      'sample' : 'sample'
    },
    1 : {
      'order': '1',
      'sample' : 'sample'
    },
    4: {
      'order': '4',
      'sample' : 'sample'
    },
    31: {
      'order': '31',
      'sample' : 'sample'
    },
    21: {
      'order': '21',
      'sample' : 'sample'
    }
  };

  final sorted = new SplayTreeMap.from(testMap, (a, b) => int.parse(testMap[a]['order']).compareTo(int.parse(testMap[b]['order'])));

  print(sorted);
}

Answer 1

A sample code on sorting Map based on it's value

import 'dart:collection';

var map = {
"a": 2,
"b": 1,
"c": -1,
};

void main() {
  final sorted = new SplayTreeMap<String,dynamic>.from(map, (a, b) => map[a] > map[b] ? 1 : -1 );
  print(sorted);
}

Answer 2

This is the easiest way for sorting maps by keys in dart.

var map = {
"a": 1,
"c": 3,
"b": 2,
};

void main() {
  final sorted = Map.fromEntries(map.entries.toList()..sort((e1, e2) => e1.key.compareTo(e2.key)));
  print(sorted);
}