List<E> constructor Null safety
- [int? length]
Creates a list of the given length.
This constructor will throw an exception if E
is not a nullable type.
In this case, another constructor such as List.filled must be used
instead.
The created list is fixed-length if length
is provided.
List fixedLengthList = new List(3);
fixedLengthList.length; // 3
fixedLengthList.length = 1; // Error
The list has length 0 and is growable if length
is omitted.
List growableList = [];
growableList.length; // 0;
growableList.length = 3;
To create a growable list with a given length, for a nullable element type, just assign the length right after creation:
List growableList = []..length = 500;
For a non-nullable element type, an alternative is the following:
List<int> growableList = List<int>.filled(500, 0, growable: true);
The length
must not be negative or null, if it is provided.
If the element type is not nullable, length
must not be greater than
zero.
This constructor cannot be used in null-safe code.
Use List.filled to create a non-empty list.
This requires a fill value to initialize the list elements with.
To create an empty list, use []
for a growable list or
List.empty
for a fixed length list (or where growability is determined
at run-time).
Implementation
external factory List([int? length]);