Dart How to get the “value” of an enum

Question

Before enums were available in Dart I wrote some cumbersome and hard to maintain code to simulate enums and now want to simplify it. I need to get the value of the enum as

Answer 1

Dart 2.7 comes with new feature called Extension methods. Now you can write your own methods for Enum as simple as that!

enum Day { monday, tuesday }

extension ParseToString on Day {
  String toShortString() {
    return this.toString().split('.').last;
  }
}

main() {
  Day monday = Day.monday;
  print(monday.toShortString()); //prints 'monday'
}

Answer 2

There is a more elegant solution:

enum SomeStatus {
  element1,
  element2,
  element3,
  element4,
}

const Map<SomeStatus, String> SomeStatusName = {
  SomeStatus.element1: "Element 1",
  SomeStatus.element2: "Element 2",
  SomeStatus.element3: "Element 3",
  SomeStatus.element4: "Element 4",
};

print(SomeStatusName[SomeStatus.element2]) // prints: "Element 2"

Answer 3

I had the same problem in one of my projects and existing solutions were not very clean and it didn't support advanced features like json serialization/deserialization.

Flutter natively doesn't currently support enum with values, however, I managed to develop a helper package Vnum using class and reflectors implementation to overcome this issue.

Address to the repository:

https://github.com/AmirKamali/Flutter_Vnum

To answer your problem using Vnum, you could implement your code as below:

@VnumDefinition
class Visibility extends Vnum<String> {
  static const VISIBLE = const Visibility.define("VISIBLE");
  static const COLLAPSED = const Visibility.define("COLLAPSED");
  static const HIDDEN = const Visibility.define("HIDDEN");

  const Visibility.define(String fromValue) : super.define(fromValue);
  factory Visibility(String value) => Vnum.fromValue(value,Visibility);
}

You can use it like :

var visibility = Visibility('COLLAPSED');
print(visibility.value);

There's more documentation in the github repo, hope it helps you out.

Answer 4

This is your enum:

enum Day {
  monday,
  tuesday,
}

Create an extension (may need to import 'package:flutter/foundation.dart';)

extension DayEx on Day {
  String get inString => describeEnum(this);
}

Usage:

void main() {
  Day monday = Day.monday;
  String inString = monday.inString; // 'monday'
}

Answer 5

Sadly, you are correct that the toString method returns "day.MONDAY", and not the more useful "MONDAY". You can get the rest of the string as:

day theDay = day.MONDAY;      
print(theDay.toString().substring(theDay.toString().indexOf('.') + 1));

Hardly convenient, admittedly.

If you want to iterate all the values, you can do it using day.values:

for (day theDay in day.values) {
  print(theDay);
}

Answer 6

enum day {MONDAY, TUESDAY}
print( 'Today is ${describeEnum(day.MONDAY)}' );

console output: Today is MONDAY