Dart: Sorting Entries of a Map by Its Values

Updated: March 31, 2023 By: A Goodman Post a comment

Imagine your boss gives you a Dart map like so:

final Map<String, int> myMap = {
  'a': 10, 
  'b': 20, 
  'c': 15, 
  'd': 5, 
  'e': 14
};

And then, he asks you to sort the map in the ascending/descending order of the map’s values. How do you solve this problem to make him happy? Well, the solution is quite simple. Let’s see the two examples below.

Table Of Contents

1 Sorting the map in ascending order of its values

2 Sorting the map in descending order of its values

Sorting the map in ascending order of its values

The code:

// KindaCode.com
void main() {
  final Map<String, int> myMap = {'a': 10, 'b': 20, 'c': 15, 'd': 5, 'e': 14};

  // sort the map in the ascending order of values

  // turn the map into a list of entries
  List<MapEntry<String, int>> mapEntries = myMap.entries.toList();

  // sort the list
  mapEntries.sort((a, b) => a.value.compareTo(b.value));

  // turn the list back into a map
  final Map<String, int> sortedMapAsc = Map.fromEntries(mapEntries);

  // print the result
  print(sortedMapAsc);
}

Output:

{d: 5, a: 10, e: 14, c: 15, b: 20}

Sorting the map in descending order of its values

The code is almost the same as the preceding example except that we change this line:

mapEntries.sort((a, b) => a.value.compareTo(b.value));

To this:

mapEntries.sort((a, b) => b.value.compareTo(a.value));

Here’s the full code:

// KindaCode.com
void main() {
  final Map<String, int> myMap = {'a': 10, 'b': 20, 'c': 15, 'd': 5, 'e': 14};

  // sort the map in the ascending order of values

  // turn the map into a list of entries
  List<MapEntry<String, int>> mapEntries = myMap.entries.toList();

  // sort the list in descending order of values
  mapEntries.sort((a, b) => b.value.compareTo(a.value));

  // turn the list back into a map
  final Map<String, int> sortedMapAsc = Map.fromEntries(mapEntries);

  // print the result
  print(sortedMapAsc);
}

Output: