dart_class.dart

dart_class.dart

/// class
class Pesron {
  String name; // field
  int age;

  String description() {
    // method
    return '$name, age: $age';
  }
}

/// User class extends Pesron
class User extends Pesron {
  String email;
}

/// Class can inplement othr class or abstract class
class CommonUser implements Pesron {
  String name;
  int age;
  String email;

  @override
  String description() {
    // method
    return '$name, age: $age, $email';
  }
}

/// Simple enum
enum Role {
  admin, // Role.admin.index == 0
  client, // Role.client.index == 1
  guest, // Role.guest.index == 2
}

/// Abstract class
abstract class GetRole {
  List<Role> get roles;
  set roles(List<Role> roles);

  // metods can be used

}

// Multiple implementations of User

class ClientUser extends User implements GetRole {
  List<Role> _roles = [Role.client];

  @override
  List<Role> get roles =>
      _roles; // avoid to wrap fields to getters and settrrs just to be "safe"

  @override
  set roles(List<Role> roles) {
    _roles = roles;
  }
}

class AdminUser extends User implements GetRole {
  @override
  List<Role> roles = [Role.guest];
}

class GuestUser extends User implements GetRole {
  final String guestNotes;

  GuestUser({name, email, age, this.guestNotes}) {
    this.name = name;
    this.email = email;
    this.age = age;
  }

  @override
  List<Role> roles = [Role.guest];
}



class DefaultUser extends GuestUser {
  /// Default constructor
  DefaultUser({String name = 'Guest', String email: 'no', int age})
      : super(name: name, email: email, age: age);

  /// named constructor
  DefaultUser.withName(String name) : super(name: name);
  
  /// factory
  factory DefaultUser.name(String name) {
    return DefaultUser(name: name);
  }
}


/// Recomendation for models
/// Use final fields and named parameters in constructor
/// Protect your models from mutation
/// you could use @immutable, for meta package
class UserEntity {
  final String name;
  final int age;
  final String email;

  UserEntity({this.name, this.age, this.email});
  
  @override
  String toString() { // reuse toString
    return '$name, age: $age, $email';
  }
}

main() {
  final u1 = User()
    ..name = 'Alex' // You could use cascade notation for mutable fields
    ..email = 'alex@gmail.com'
    ..age = 20;
  print(u1.description());
  final guest = DefaultUser.name('Guest 1');
  print(guest.description());
  
  final userEntity = UserEntity(
    name: 'Alex',
    email: 'alex@gmail.com',
    age: 20,
  );
  print(userEntity);
}