Map<K, V>.unmodifiable constructor Null safety

Map<K, V>.unmodifiable(
  1. Map other

Creates an unmodifiable hash-based map containing the entries of other.

The keys must all be instances of K and the values of V. The other map itself can have any type.

The map requires the keys to implement compatible operator== and hashCode. The created map iterates keys in a fixed order, preserving the order provided by other.

The resulting map behaves like the result of Map.from, except that the map returned by this constructor is not modifiable.

final planets = <int, String>{1: 'Mercury', 2: 'Venus', 3: 'Earth'};
final unmodifiableMap = Map.unmodifiable(planets);
unmodifiableMap[4] = 'Mars'; // Throws


external factory Map.unmodifiable(Map<dynamic, dynamic> other);