abstract class Vehicle {
  factory Vehicle(String type, String model) {
    if(type == 'car') return  Car(model);
    if(type == 'moto') return  Moto(model);
    throw 'can\'t create type $type';
  }
  String get modelName;
}

class Car implements Vehicle {
  final String model;
  Car(this.model);
  String get modelName => model;
}

class Moto implements Vehicle {
  final String model;
  Moto(this.model);
  String get modelName => model;
}

void main() {
  try {
    final v1 = Vehicle('car', 'mercedes');
    final v2 = Vehicle('moto', 'harley');
    print(v1.modelName);
    print(v2.modelName);
  } catch(err) {
    print('i am in the catch close.');
    print(err);
  }
}