Dart Equatable Package: Simplify Equality Comparisons
If you’ve been writing Dart, chances are you’ve had to override the == operator and hashCode in order to compare different instances of the same class.
Say we have a class Person which looks something like this:
We can create an instance of a Person like so:
As we build our application there are many scenarios in which we want to be able to compare different instances of a Person for equality such as in test expectations or in Stream transformations like distinct.
If you try to run the following code you’ll see that two instances of Person with the exact same name and age are not equal.
This is because by default, two objects are only equal if they are the exact same object (Dart Documentation). In the above snippet, bob is a different object with a different hashCode and identity so when we compare bob with a new instance of a Person Dart will treat them as not equal.
In order to be able to compare different instances of a Person we would need to override the == operator (and consequently hashCode). As a result our Person class would look something like:
Now if we run the following code again:
print(bob == Person(name: “Bob”, age: 40)); // trueWe are able to compare different instances of `Person`.
You can probably already see how this can quickly become a pain 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.
There are other packages that will actually generate the boilerplate for you; however, you still have to run the code generation step which is not ideal.
With Equatable there are no extra steps needed so we can focus more on writing amazing applications and save ourselves the headache of having to generate/write a ton of boilerplate code.
To use Equatable, we need to add it as a dependency to our pubspec.yaml
dependencies:
equatable: ^0.6.0Then install it
# Dart
pub get# Flutter
flutter packages get
and lastly extend Equatable
We significantly reduced the amount of boilerplate which is pretty awesome, and we didn’t have to deal with the complex overrides or code generation.
To see Equatable in action, you can check out the bloc package examples (flutter_login or flutter_infinite_list) or checkout the articles for more details (flutter login, flutter_infinite_list).
You can support me by ⭐️the repository, or 👏 for this story, thanks!
