dart-fact_constr-fact_patt.dart

class Vehicle{

  factory Vehicle(int numberOfTyres) {
    // An if-else statement can be used too
    switch (numberOfTyres) {
      case 2:
        return Motorcycle();
      case 3:
        return Tricycle();
      case 4:
        return Car();
      default:
        throw Error();
    }
  }

  start(){}
  accelerate(){}
  stop(){}
}

class Motorcycle implements Vehicle{
  
  // Default Motorcycle constructor
  Motorcycle(){
    // blah.. An empty constructor will feel lonely so..
    print('Motorcycle created');
  }

  start(){}
  accelerate(){}
  stop(){}
}

class Tricycle implements Vehicle{
  
  // Default Tricycle constructor
  Tricycle(){
    // blah.. An empty constructor will feel lonely so..
    print('Tricycle created');
  }
  
  start(){}
  accelerate(){}
  stop(){}
}

class Car implements Vehicle{
  
  // Default Car constructor
  Car(){
    // blah.. An empty constructor will feel lonely so..
    print('Car created');
  }
  start(){}
  accelerate(){}
  stop(){}
}

void main() {
  Vehicle(2);
  Vehicle(3);
  Vehicle(4);
}