Map that you can use like Python's collections.defaultdict

Features

Specify the default value of Map. This DefaultMap will never return null.

Usage

Simply instantiate DefaultMap.

final DefaultMap<int, String> m = DefaultMap<int, String>();
    m[1] = 'one';
    print(m[1]); // 'one'
    print(m[2]); // ''

You may need to give an argument, ifAbsent, which is a function to defines the default value. In this case, the argument is () => HashMap<int, int>(), meaning an empty HashMap<int, int> is returned when keys don't exist.

    final DefaultMap<int, HashMap<int, int>> m =
        DefaultMap<int, HashMap<int, int>>(() => HashMap<int, int>());
    m[1][1] = 1;
    print(m[1]); // {1: 1}
    print(m[2]); // {} 

Additional information

If your V in DefaultMap<K, V> is included below, you don't need to specify the default value (the argument, ifAbsent).