A more advanced alternative to Dart's native Map implementation. All operations that fetch an element from the Dictionary returns an Option type. If the fetched value existed then the Option type returned will be Some and will have the value wrapped inside. If the key was not found in the Dictionary then the Option type returned will be None.

We returning Option types instead of raw values is you can focus more on the composition and flow of your logic instead of worrying about defensive Map#containsKey safety checks.

Tested with Dart 1.12.1


import 'package:dict/dict.dart';

main() {
  var dict = new Dictionary.fromMap({
    'A': 'a',
    'B': 'b',
    'C': 'c'

  var other = new Dictionary.fromMap({
    'C': 'c',
    'D': 'd',
    'E': 'e'

  var lowerA = dict.getOrDefault('A', 'N/A');
  var lowerB = dict['B'].getOrDefault('N/A');
  var lowerC = dict.get('C').getOrDefault('N/A');
  var findA = dict.findKey((v, k) => k == 'A').getOrDefault('N/A');
  var findB = dict.findValue((v, k) => v == 'b').getOrDefault('N/A');
  var findBs = dict.partition((v, k) => v == 'b');
  var mapped = dict.map((v, k) => v + " - mapped");
  var byValue = dict.groupBy((v, k) => v);
  var diffKey = dict.differenceKey(other);
  var diffVal = dict.difference(other);
  var interKey = dict.intersectionKey(other);
  var interVal = dict.intersection(other);
  var merged = dict.merge(other);
  var reduced = dict.reduce((memo, v, k) => memo + v);
  var folded = dict.fold(new Dictionary(), (memo, v, k) {
    memo[k] = v + " - folded";
    return memo;

Features and bugs

Please file feature requests and bugs at the issue tracker.