Dart class as enum template

enum_template.dart

void main() {
  print(Number.one);
  print(Number.two);
  print(Number.three);

  print(Number.fromInt(1));
  print(Number.fromInt(2));
  print(Number.fromInt(3));

  print(Number.fromString('1'));
  print(Number.fromString('2'));
  print(Number.fromString('3'));
  
  print(Number.fromString('4')); // Uncaught Error: Invalid argument(s): Invalid Number: 4
}

class Number {
  // possible enum values
  static const one = Number._('one', 1);
  static const two = Number._('two', 2);
  static const three = Number._('three', 3);

  // public enum fields
  final int value;

  // string representation of enum value
  final String _string;

  // private const constructor
  const Number._(this._string, this.value);

  // mappable values
  static const _values = {1: one, 2: two, 3: three};

  // factories
  factory Number.fromInt(int value) => _values[value] ?? (throw ArgumentError('Invalid Number: $value'));

  factory Number.fromString(String value) => Number.fromInt(int.parse(value));

  @override
  String toString() => '$runtimeType.$_string';
}