Enums in Dart

What are Enums?

An enum (enumeration) is a type with a fixed set of named constant values. Enums make code more readable and type-safe by replacing magic strings or integers with meaningful names.

Basic Enums

enum Direction { north, south, east, west }
enum Status { active, inactive, pending, banned }
enum Color { red, green, blue }

void main() {
  Direction dir = Direction.north;
  print(dir);           // Direction.north
  print(dir.name);      // north
  print(dir.index);     // 0

  // All values
  print(Direction.values);  // [Direction.north, Direction.south, ...]
}

Enhanced Enums (Dart 2.17+)

Dart 2.17+ allows enums to have fields, methods, and constructors:

enum Planet {
  mercury(3.7),
  venus(8.87),
  earth(9.81),
  mars(3.72);

  final double gravity;  // m/s²
  const Planet(this.gravity);

  double weightOn(double mass) => mass * gravity;
}

void main() {
  double myMass = 70.0;  // kg on Earth
  for (var planet in Planet.values) {
    print('Weight on $${planet.name}: '
          '$${planet.weightOn(myMass).toStringAsFixed(1)} N');
  }
}

Weight on mercury: 259.0 N
Weight on venus: 620.9 N
Weight on earth: 686.7 N
Weight on mars: 260.4 N

Enums in Switch

Status userStatus = Status.pending;

switch (userStatus) {
  case Status.active:
    print('User is active');
    break;
  case Status.pending:
    print('Awaiting approval');
    break;
  case Status.banned:
    print('Access denied');
    break;
  default:
    print('Unknown status');
}

// Dart 3 pattern matching switch:
String label = switch (userStatus) {
  Status.active   => 'Active',
  Status.inactive => 'Inactive',
  Status.pending  => 'Pending',
  Status.banned   => 'Banned',
};

🧠 Quiz

Summary

Enums define a fixed set of named constants. Use enum.name for the string name, enum.index for position, and Enum.values for all constants. Dart 2.17+ enhanced enums support fields, methods, and constructors. Use enums in switch statements for exhaustive pattern matching.