Enum from String

Question

I have an Enum and a function to create it from a String because i couldn\'t find a built in way to do it

Answer 1

Here is an alternative way to @mbartn's approach using extensions, extending the enum itself instead of String.

Faster, but more tedious

// We're adding a 'from' entry just to avoid having to use Fruit.apple['banana'],
// which looks confusing.
enum Fruit { from, apple, banana }

extension FruitIndex on Fruit {
  // Overload the [] getter to get the name of the fruit.
  operator[](String key) => (name){
    switch(name) {
      case 'banana': return Fruit.banana;
      case 'apple':  return Fruit.apple;
      default:       throw RangeError("enum Fruit contains no value '$name'");
    }
  }(key);
}

void main() {
  Fruit f = Fruit.from["banana"];
  print("$f is ${f.runtimeType}"); // Outputs: Fruit.banana is Fruit
}

Less tedius, but slower

If O(n) performance is acceptable you could also incorporate @Collin Jackson's answer:

// We're adding a 'from' entry just to avoid having to use Fruit.apple['banana']
// which looks confusing.
enum Fruit { from, apple, banana }

extension FruitIndex on Fruit {
  // Overload the [] getter to get the name of the fruit.
  operator[](String key) =>
    Fruit.values.firstWhere((e) => e.toString() == 'Fruit.' + key);
}

void main() {
  Fruit f = Fruit.from["banana"];
  print("$f is ${f.runtimeType}"); // Outputs: Fruit.banana is Fruit
}