What methods allow ensuring the uniqueness of elements when using a set data structure?

In Flutter (Dart), the following methods are used to ensure the uniqueness of elements in a data structure Set:

• Using the built-in Set type, which by default stores unique elements. When adding an element, its equality with existing elements is checked.
• Overriding the == and hashCode methods in custom classes. This is necessary for the Set to correctly compare objects and determine their uniqueness.

Example:

class Person {
  final String name;
  final int id;

  Person(this.name, this.id);

  @override
  bool operator ==(Object other) =>
      identical(this, other) ||
      other is Person && runtimeType == other.runtimeType && id == other.id;

  @override
  int get hashCode => id.hashCode;
}

void main() {
  var people = <Person>{};
  people.add(Person('Alice', 1));
  people.add(Person('Bob', 2));
  people.add(Person('Alice', 1)); // will not be added, as id matches

  print(people.length); // 2
}

Thus, uniqueness is ensured by correct implementation of object comparison and hashing.