Pattern matching 4

readme.md

Pattern matching 4

Created with <3 with dartpad.dev.

main.dart

class CarPart {
  const CarPart();

  // METHOD COULD BE GENERATED
  T match<T>({
    required T Function(Engine v) engine,
    required T Function(Transmission v) transmission,
  }) {
    // ignore_for_file: curly_braces_in_flow_control_structures
    if (this is Engine) return engine(this as Engine);
    else return transmission(this as Transmission); 
  }
}

class Engine extends CarPart {
  const Engine({
    required this.cylinders,
    required this.horsepower,
  });
  final int cylinders;
  final int horsepower;
}

class Transmission extends CarPart {
  const Transmission({
    required this.gears,
    required this.isManual,
  });
  final int gears;
  final bool isManual;
}

class Car {
  const Car(
    this.model, {
    required this.parts,
  });
  final String model;
  final List<CarPart> parts;

  String get description => [
        'These are the parts in a $model:',
        for (final part in parts) '- ${_getDescriptionForCarPart(part)}',
        '- And a whole bunch of other parts which I was too lazy to mention.',
      ].join('\n');
}

String _getDescriptionForCarPart(CarPart part) => part.match(
  engine: (v) => 'A ${v.cylinders} cylinder engine '
        'which makes ${v.horsepower}hp.',
  transmission: (v) => 'A ${v.gears} speed '
        '${v.isManual ? 'manual' : 'automatic'} transmission.',
);

void main(List<String> args) => print(
    const Car(
      'Nissan Skyline GT-R',
      parts: [
        Engine(cylinders: 6, horsepower: 300),
        Transmission(gears: 7, isManual: true),
      ],
    ).description,
  );