How to create a sequence number in a list in Dart or Flutter | Dart By Example

Sometimes, there’s a need to generate a fixed list containing a sequence of numbers from 0 to N. This article demonstrates multiple methods to achieve this in Dart or Flutter.

#How to Create a Sequence of Numbers List for a Given Number in Dart or Flutter

There are several approaches to creating a sequence of numbers in a list.

• Using the generate() function

The generate() function within a list creates a list with values generated by a specified function.

Syntax:

List generate(length, Function, {growable})

The list is created with a length attribute. Function is a generator function logic to populate the list with values. The growable parameter, when set to false, indicates that the List is fixed in size.

Here’s an example to create a list of sequence numbers from 0 to N.

void main() {
  var sequenceNumbers = new List<int>.generate(20, (k) => k + 1);
  print(sequenceNumbers);
}

Output:

[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20]

• Using Collection For The collection for syntax in Dart is utilized to create a list by iterating over indexed values.

void main() {
  var numberList = [for (var i = 1; i <= 20; i++) i];
  print(numberList);
}

Output:

[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20]

#Conclusion

In conclusion, creating a sequence of numbers in a list is straightforward with the generate() function and collection for in Dart, as demonstrated in the examples above.