xdart-test/lib/Bicycle.dart

class Bicycle {
  int age;

  Bicycle({this.age});

  factory Bicycle.fromJson(Map<String, dynamic> json) {
    return Bicycle(
      age: json['age'],
    );
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['age'] = this.age;
    return data;
  }
}