How to flatMap a list of lists in Flutter

Introduction

Sometimes, we may wish to flatMap a list of lists in Flutter/Dart. In this post, we'll learn how to do it.

How to flatMap a list of lists in Flutter

To flatten a list of lists in Flutter/Dart we can use forEach() or expand() method:

Flatten a list of lists in Flutter using forEach() method

var listOfLists = [[1, 2], [3, 4], [5, 6]];

var flatten = [];
listOfLists.forEach((nums) => nums.forEach((number) => flatten.add(number)));
print(flatten);

The output:

[1, 2, 3, 4, 5, 6]

Flatten a list of lists using expand() method

var listOfLists = [[1, 2], [3, 4], [5, 6]];

var flatten = listOfLists.expand((number) => number).toList();
print(flatten);

The output:

[1, 2, 3, 4, 5, 6]

Conclusion

In this article, we showed how to flatMap a list of lists in Flutter/Dart.