commit | 11b26ba7121494baca99dad4d9e67a96e72fed6e | [log] [tgz] |
---|---|---|
author | Felix Angelov <felangelov@gmail.com> | Tue Oct 15 21:48:00 2024 -0500 |
committer | Felix Angelov <felangelov@gmail.com> | Tue Oct 15 21:48:00 2024 -0500 |
tree | 9d4f1922b5f3fcaeb4ef7390580cde45757c0f1a | |
parent | 6ddd3f08820ec80a685416603c4a6cf8715f8a53 [diff] |
chore: v3.0.0-dev.1
Being able to compare objects in Dart
often involves having to override the ==
operator as well as hashCode
.
Not only is it verbose and tedious, but failure to do so can lead to inefficient code which does not behave as we expect.
By default, ==
returns true if two objects are the same instance.
Let's say we have the following class:
class Person { const Person(this.name); final String name; }
We can create instances of Person
like so:
void main() { final Person bob = Person("Bob"); }
Later if we try to compare two instances of Person
either in our production code or in our tests we will run into a problem.
print(bob == Person("Bob")); // false
For more information about this, you can check out the official Dart Documentation.
In order to be able to compare two instances of Person
we need to change our class to override ==
and hashCode
like so:
class Person { const Person(this.name); final String name; @override bool operator ==(Object other) => identical(this, other) || other is Person && runtimeType == other.runtimeType && name == other.name; @override int get hashCode => name.hashCode; }
Now if we run the following code again:
print(bob == Person("Bob")); // true
it will be able to compare different instances of Person
.
You can see how this can quickly become a hassle when dealing with complex classes. This is where Equatable
comes in!
Equatable
overrides ==
and hashCode
for you so you don't have to waste your time writing lots of boilerplate code.
First, we need to do add equatable
to the dependencies of the pubspec.yaml
dependencies: equatable: ^3.0.0-dev.0
Next, we need to install it:
# Dart dart pub get # Flutter flutter packages get
Lastly, we need to add the @Equatable
annotation.
import 'package:equatable/equatable.dart'; @Equatable() class Person { const Person(this.name); final String name; }
We can now compare instances of Person
just like before without the pain of having to write all of that boilerplate. Note: Equatable is designed to only work with immutable objects so all member variables must be final (This is not just a feature of Equatable
- overriding a hashCode
with a mutable value can break hash-based collections).
class Person { const Person(this.name); final String name; @override bool operator ==(Object other) => identical(this, other) || other is Person && runtimeType == other.runtimeType && name == other.name; @override int get hashCode => name.hashCode; }
import 'package:equatable/equatable.dart'; @Equatable() class Person { const Person(this.name); final String name; }
You can check out and run performance benchmarks by heading over to benchmarks;