How to combine lists using the expand() method in Dart

Method

The expand() method in Dart can add all the elements of a list one by one to a new list. It is typically used to combine more than two lists.

Syntax

[list1, list2, list3].expand(x => x)

Note: Any variable name can be used in the place of x.

Return value

An iterable is returned.

Code

main() {
    
  // Creating lists
  List basket1 = ['Mango', 'Apple'];
  List basket2 = ['Orange', 'Avocado', 'Grape'];
  List basket3 = ['Lemon'];
    
  // converting the lists to an iterable
  var newBasketIterable = [basket1, basket2, basket3].expand((x) => x);
  // combining the lists 
  var newBasket = newBasketIterable.toList();
    
  // printing the iterable
  print("Iterable:  $newBasketIterable");
  // printing the combined list
  print("Combined List:  $newBasket");
 
}

Explanation

  • Lines 4 to 6: We create three lists named basket1, basket2, and basket3.

  • Lines 9 to 11: We combine each item in the lists using the expand() method, and then pass the toList() method to convert to a list. The result is stored in a new list named newBasket.

  • Line 14: We print newBasketIterable, the iterable containing the elements of the three lists declared above.

  • Line 16: We print newBasket, the list containing the combined elements of the three lists declared above.

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