Step 1 - Basic mixin

mixin Timestamped {
  DateTime get stampedAt => DateTime.now();
}

class Event with Timestamped {
  final String name;
  Event(this.name);
}

void main() {
  Event e = Event('login');
  print('${e.name} at ${e.stampedAt}');
}

Step 2 - Mixin with dependency on class

class Model {
  String id = 'x';
}

mixin Pretty on Model {
  String describe() => 'Model($id)';
}

class User extends Model with Pretty {}

void main() {
  User u = User();
  print(u.describe());
}

• on Model means Pretty may only be applied to types that are Model (or subclass), so id is safe to use.

Step 3 - Order: extends then with

class Base {}
mixin M1 {}
mixin M2 {}

class C extends Base with M1, M2 {}

Good habit

• Prefer composition for large state; mixins for small cross-cutting slices (logging, serialization hooks, equality helpers).

Practice tasks

• Add a mixin Identified that requires String get id via on and implements bool sameAs(Identified other) => id == other.id.
• Apply two mixins to one class and call methods from both.