Introduction
In Flutter/Dart, we may need to initialize a List with values. In this article, we present several methods of how to do it.
How to initialize List with values in Flutter
In Flutter we can initialize a list simply using the []
operator:
List<int> list1 = [40, 30, 20, 10];
print(list1);
var list2 = ['first', 'second', 3, 4];
print(list2);
The output:
[40, 30, 20, 10]
[first, second, 3, 4]
To initialize a fixed-size list in Flutter we can use the filled()
constructor:
var listWithFixedSize = List.filled(1, 2, 3); // we cannot add any more items to that list
print(listWithFixedSize);
The output:
[1, 2, 3]
To initialize a growable list in Flutter we use the filled()
constructor with the growable: true
attribute:
var thisIsGrowableList = List.filled(1, 2, 3, growable: true);
thisIsGrowableList.add(4);
print(thisIsGrowableList);
The output:
[1, 2, 3, 4]
To initialize a list in Flutter we can also use the from()
constructor that works similar to filled()
:
var listWithFixedSize = List.from([1, 2, 3], growable: false); // we cannot add any more items to that list
print(listWithFixedSize);
var thisIsGrowableList = List.from([1, 2, 3]);
thisIsGrowableList.add(4);
print(thisIsGrowableList);
The output:
[1, 2, 3]
[1, 2, 3, 4]
The difference between filled()
and from()
constructor is that filled()
by default creates fixed-size
list and from()
creates by default growable
list.
In Flutter there is also a constructor generate()
that can be used to create a list of items:
var sampleList = List.generate(4, (index) => index * 2);
print(sampleList);
The output:
[0, 2, 4, 6]
Conclusion
In this short article, we presented methods to initialize a list in Flutter/Dart.
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