How do I compare two lists as being equal and containing the same objects, in Dart?

Question

I have two lists:

List fruits = ['apples', 'bananas'];
List foods = ['apples', 'bananas'];

How can I compare fruits and foods and ensure that both lists have the same objects in the same order?

Answer 1

The recommended way to compare lists for equality (rather than identity) is by using the Equality classes from the following package

import 'package:collection/equality.dart';

E.g.,

Function eq = const ListEquality().equals;
print(eq(fruits, foods)); // => true

This works for your case because the fruits and foods contain corresponding arguments that are identical(). If you want to (deeply) compare lists that might contain other collections then instead use:

Function deepEq = const DeepCollectionEquality().equals;
List list1 = [1, ['a',[]], 3];
List list2 = [1, ['a',[]], 3];
print(    eq(list1, list2)); // => false
print(deepEq(list1, list2)); // => true

There are other Equality classes that can be combined in many ways, including equality for Maps. You can even perform an unordered (deep) comparison of collections:

Function deepEq = const DeepCollectionEquality.unordered().equals;

For details see the package API documentation. As usual, to use such a package you must list it in your pubspec.yaml:

dependencies:
  collection: any