How to Flatten a Nested List in Dart

In Dart, you can use the expand() method is to look for nested collections inside your collection and flatten them into a single list.

Example:

// https://www.kindacode.com
// main.dart
void main() {
  final matrix = [
    [1, 2, 3],
    [4, 5, 6],
    [7, 8, 9],
  ];

  final linear = matrix.expand((element) => element).toList();
  print(linear);
}

Output:

[1, 2, 3, 4, 5, 6, 7, 8, 9]

Further reading:

• Flutter & Dart: Displaying Large Numbers with Digit Grouping
• Using Static Methods in Dart and Flutter
• Dart: How to Update a Map
• Dart & Flutter: 2 Ways to Count Words in a String
• Conditional (Ternary) Operator in Dart and Flutter
• Using GetX to make GET/POST requests in Flutter

You can also take a tour around our Flutter topic page and Dart topic page to see the latest tutorials and examples.