Immutability #

Mutable class #

/*
  __  __      _        _    _
 |  \/  |_  _| |_ __ _| |__| |___
 | |\/| | || |  _/ _` | '_ \ / -_)
 |_|  |_|\_,_|\__\__,_|_.__/_\___|
*/
class Person {
  String firstName;
  String lastName;
  Person({required this.firstName, required this.lastName});

  toString() => "$firstName $lastName";
}

void main() {
  final p1 = Person(firstName: "Alice", lastName: "Smith");
  print("p1: $p1");
  final p2 = changeName(p1, lastName: 'Carpenter');
  print("p1: $p1");
  print("p2: $p2");
  print("Are p1 and p2 identical? ${identical(p1, p2)}");
}

Person changeName(Person person, {required String lastName}) {
  person.lastName = lastName;
  return person;
}

Immutable class #

/*
  ___                 _        _    _
 |_ _|_ __  _ __ _  _| |_ __ _| |__| |___
  | || '  \| '  \ || |  _/ _` | '_ \ / -_)
 |___|_|_|_|_|_|_\_,_|\__\__,_|_.__/_\___|
*/
class Person {
  final String firstName;
  final String lastName;
  const Person({required this.firstName, required this.lastName});

  toString() => "$firstName $lastName";
}

void main() {
  final p1 = Person(firstName: "Alice", lastName: "Smith");
  print("p1: $p1");
  final p2 = changeName(p1, lastName: 'Carpenter');
  print("p1: $p1");
  print("p2: $p2");
  print("Are p1 and p2 identical? ${identical(p1, p2)}");
}

Person changeName(Person person, {required String lastName}) {
  return Person(firstName: person.firstName, lastName: lastName);
}