Dart .addAll()

The .addAll() method in Dart is used to add multiple elements from one list to another. This method is useful for combining the contents of multiple lists into a single list. This method does not create a new list but rather, it modifies the original list.

Syntax

list1.addAll(list2);

• list1: The list to which another list is to be added.
• list2: The list to be added to list1.

Example

In the following example, there are three operations that are carried out using the .addAll() method:

• The first operation appends a list [4, 5, 6] to an existing list nums.
• The second operation combines the lists otherNumbers and extraNumbers and appends them to the numbers list.
• The third operation appends a list additionalElements to a fixed-length list nonGrowableList.

Here is the example demonstrating the usage of the .addAll() method in Dart:

void main() {
  final nums = <int>[1, 2, 3];
  //Appends the list to the end of the 'nums' list
  nums.addAll([4, 5, 6]);
  print(nums);

  List<int> numbers = [1, 2, 3];
  Set<int> otherNumbers = {4, 5, 6};
  List<int> extraNumbers = [7, 8, 9];

  //Appends the lists 'otherNumbers' and 'extraNumbers' to the end of the 'numbers' list.
  numbers.addAll([...otherNumbers, ...extraNumbers]);
  print(numbers);

  List<int> nonGrowableList = List<int>.filled(3, 0);
  List<int> additionalElements = [4, 5, 6];

  //Appends a list to the end of a fixed-length list
  nonGrowableList.addAll(additionalElements);
  print(nonGrowableList);
}

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The output for the above code is:

[1, 2, 3, 4, 5, 6]
[1, 2, 3, 4, 5, 6, 7, 8, 9]
Uncaught Error: Unsupported operation: addAll

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Note - The .addAll() method only works on a growable list. If the list is a fixed-length list, it throws an Unsupported operation error and retains all objects.