Simplify Equality Comparisons with Equatable in Dart

In Dart, comparing objects for equality by default relies on instance identity. To customize equality behavior, developers must manually override the == and hashCode operators, which can be tedious and error-prone.

Equatable to the Rescue

Equatable is a Dart package that simplifies equality comparisons by automatically overriding == and hashCode for immutable classes. It provides a concise and efficient way to compare objects based on their properties.

Usage

To use Equatable, import the package and extend your class from it:

import 'package:equatable/equatable.dart';

class Person extends Equatable {
  final String name;

  const Person(this.name);

  @override
  List get props => [name];
}

The props getter defines the properties used for comparison. In this example, the name property is used to determine equality.

Example

final person1 = Person("Bob");
final person2 = Person("Bob");

print(person1 == person2); // true

toString

Equatable can also implement the toString method to include the values of the properties used for comparison:

@override
bool get stringify => true;

EquatableMixin

For classes that cannot extend Equatable directly, the EquatableMixin can be used to provide similar functionality:

class EquatableDateTime extends DateTime with EquatableMixin {
  @override
  List get props => [year, month, day, hour, minute, second, millisecond, microsecond];
}

Performance

Equatable is designed to be efficient. Benchmarks show minimal overhead compared to manual equality implementations:

Conclusion

Equatable simplifies equality comparisons in Dart by automating the generation of custom equality logic. It improves code quality, reduces boilerplate, and minimizes the risk of errors. Embracing Equatable can significantly streamline the process of writing equality-based code in your Dart applications.