What is the equivalent of this python dictionary in Dart?

Question

What is the equivalent of this python dictionary in Dart?

edges = {(1, 'a') : 2,
         (2, 'a') : 2,
         (2, '1') : 3,
         (3, '1') : 3}

Answer 1

You could use package:collection's EqualityMap to define a custom hash algorithim that uses ListEquality. For example, you could do this:

var map = new EqualityMap.from(const ListEquality(), {
  [1, 'a']: 2,
  [2, 'a']: 2,
});

assert(map[[1, 'a']] == map[[1, 'a']])

This will be a heavier weight implementation of Map, though.

Answer 2

You have differents way to do this

1. Using a List

var edges = <List, num>{
  [1, 'a']: 2,
  [2, 'a']: 2,
  [2, '1']: 3,
  [3, '1']: 3
};

Simple to write, but you won't be able to retrieve data with

edges[[2, 'a']]; // null

Except if you use const

var edges = const <List, num>{
  const [1, 'a']: 2,
  const [2, 'a']: 2,
  const [2, '1']: 3,
  const [3, '1']: 3
};  

edges[const [2, 'a']]; // 2

2. Using Tuple package

https://pub.dartlang.org/packages/tuple

var edges = <Tuple2<num, String>, num>{
  new Tuple2(1, 'a'): 2,
  new Tuple2(2, 'a'): 2,
  new Tuple2(2, '1'): 3,
  new Tuple2(3, '1'): 3
}

edges[new Tuple2(2, 'a')]; // 2