Pattern matching 2

readme.md

Pattern matching 2

Created with <3 with dartpad.dev.

main.dart

class CarPart {
  const CarPart(this.type);
  final CarPartType type;
}

enum CarPartType<T extends CarPart> {
  engine<Engine>(),
  transmission<Transmission>(),
}

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

class Transmission extends CarPart {
  const Transmission({
    required this.gears,
    required this.isManual,
  }): super(CarPartType.transmission);
  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) {
  switch (part.type) {
    case CarPartType.engine:
      part as Engine;
      return 'A ${part.cylinders} cylinder engine '
          'which makes ${part.horsepower}hp.';
    default:
      part as Transmission;
      return 'A ${part.gears} speed '
            '${part.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,
    );