Dart Extensions example

dart_extensions_example.dart

/// Library A

class Animal {
  final String name;
  
  const Animal({ required this.name });
}

class Dog extends Animal {
  final String breed;
  
  const Dog({ required String name, required this.breed })
    : super(name: name);
}

/// Your program

void main() {
  final astro = Dog(name: 'Astro', breed: 'German Shephard');
  print(astro.name);
  
  astro.bark();
}

/// Library B

extension DogAction on Dog {
  
  void bark() {
    print('Woof!');
  }
  
}