Dart Collections: Arrays or LIST as Fixed-length List. Dart for Flutter #11.1

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Dart beginners guide. Explore Arrays or Fixed length List in Ordered Dart Collections. Dart supports various Collection types such as Set, Map, HashSet, HashMap, Queue, LinkedList. Let us explore each one of them in this section.

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Dart List constructor is not supported any more. You can use the following to create a fixed length list now:
List<int?> numbersList = List<int?>.filled(5, null);

int? implies the list items can be null.

If you want the default value to be 0 and that the list shouldn't have null value, use this instead:
List<int> numbersList = List<int>.filled(5, 0);

annapurnasid

To people facing the same issue :
Reason:
In modern Dart, when we write List<int> Dart considers this as a List of integers but we know that in Dart, variables without any value are null!
so that's where the problem arises List of integers with a null value in it,

Solution:
Use this instead, i.e. pre-populate the array: -
List<int> numberList = List.filled(5, -1); // -1 can be any integer number

harshrishiwal

Great tutorial but this section on fixed length list and the growable list section is deprecated and not applicable anymore? I'm very new to dart so any errors & omission excepted :-). just sharing info...full source codes below:-

new fixed length list:-
// <int?> is to allow null values assignment
List<int?> numbersList = List<int?>.filled(5, 0, growable: false);
numbersList[0] = 73;
numbersList[1] = 21;
numbersList[2] = 64;
numbersList[3] = 73;
numbersList[4] = 12;
numbersList[1] = null;
print(numbersList); //console: [73, null, 64, 73, 12]

// above list not iterable!!
// to iterate then use below:-
List<int> numbersList2 = [1, 2, 3, 4, 5];

for (int e in numbersList2) {
print(e);
}
//using forEach
print('forEach : $element'));

full
void main() {
// fixed length
//List<int> numbersList = List(5); deprecated, use below for fixed length
List<int?> numbersList = List<int?>.filled(5, 0, growable: false);
numbersList[0] = 73;
numbersList[1] = 21;
numbersList[2] = 64;
numbersList[3] = 73;
numbersList[4] = 12;

numbersList[1] = null;
//myList.add('bbb'); can't use add because not growable
print(numbersList);
for (int i = 0; i < numbersList.length; i++) {
print(numbersList[i]);
}
//for (int element in numbersList) {
// print(element);
//}

List<int> numbersList2 = [1, 2, 3, 4, 5];
//growable
for (int e in numbersList2) {
print(e);
}

print('forEach : $element'));
}

Wongmc

Sir please my one error in list
The default list constructor is not available
When null safety is enabled

AnilPawar-lpzd

## FIXED LENGTH LIST
List<int> numberList = List<int>.filled(3, 0);
numberList[0] = 73;
numberList[1] = 73;
numberList[2] = 73;
print(numberList);

reycoseguma

the delete operation is not working as the error shows that can't remove from fixed length

Gurpreet-Chandi

@Smartheard, sir i am getting error through your code which i copied from github and it is saying that:- The default 'List' constructor isn't available when null safety is enabled.
I am using intellij idea, also i copy pasted the same code in dart pad but still facing the same error again and again

whitehawk

Like any other language how to take input from the user in Dart

amansarma

The 'For Loop' give errors.
cant print out the elements but giving errors.

I am using VSCode with 'Runner' as my code runner, and it is giving error.
already installed any Dart extensions and Flutter but why?

muhammadyusoffjamaluddin