[Dart] 5. 생성자

class Dog {
  String name;
  int age;
  String color;
  int thirsty;

  Dog(String name, int age, String color, int thirsty)
      : this.name = name,
        this.age = age,
        this.color = color,
        this.thirsty = thirsty;
}

class Cat {
  String name;
  int age;
  String color;
  int thirsty;

  Cat(this.name, this.age, this.color, this.thirsty);
}

class Dog {
  int age;
  String name;
// {}를 쓰면 선택해서 쓸수 있다. 선택적 매개변수
// required를 쓰면 반드시 받아야한다.
// cascade ..

  Dog({required this.age, required this.name});
}

class Cat {
  int? age;
  String? name;

  Cat({this.age, this.name = "토토"});

  void cry() {
    print("야옹");
  }
}

void main() {
  Dog d = Dog(name: "토토", age: 10);
  Cat c = Cat(age: 15)..cry();
  print("개는 : ${d}");
  print("고양이는 : ${c}");
}

class User {
  int id;
  String username;
  String password;

  User(this.id, this.username, this.password);

  User.hello(
      {required this.id, required this.username, required this.password});

  User.fromJson(Map<String, dynamic> json)
      : this.id = json["id"],
        this.username = json["username"],
        this.password = json["password"];
}

void main() {
  User u1 = User(1, "ssar", "1234");
  User u2 = User.hello(id: 1, username: "ssar", password: "1234");
  User u3 = User.fromJson({"id": 1, "username": "ssar", "password": "1234"});

  print(u1.username);
  print(u2.username);
  print(u3.username);
}