Array

Arr (Array) is a zero cost extension type of List, where the List is treated as non-growable. This is useful for correctly handling lists where growable is false and const lists - as these types of lists are treated the same in the regular Dart type system, which may lead to errors. With Arr, type intent is clear for maintainers and developers are able think about code performance more critically.

Arr<int?> array = Arr(null, 10);

Arr's allocation will be more efficient than compared to a List since it does not reserve additional capacity and allocates the full amount eagerly. Which is important since allocations account for most of the cost of the runtime costs of a List.

var array = Arr(null, 10); // Creates an array of 10 null values

From a Constant List

var array = Arr.constant(const [1, 2, 3, 4, 5]); // Creates an array from a constant list

Using a Generator Function

var array = Arr.generate(10, (i) => i); // Generates an array with values from 0 to 9

Creating a Range

var array = Arr.range(0, 10, step: 2); // Creates an array with values [0, 2, 4, 6, 8]

Accessing Elements

You can access and modify elements just like a normal list:

var entry = array[2]; // Accesses the element at index 2
array[2] = 10; // Sets the element at index 2 to 10

Iterating Over Elements

You can use a for-in loop to iterate over the elements:

for (final entry in array) {
  print(entry); // Do something with each entry
}

Converting to List

You can convert Arr back to a regular list (this will be erased at compile time so there is no cost):

var list = array.list;

Splitting Arrays

You can split an array into two slices:

var (slice1, slice2) = array.splitSlice(3); // Splits the array at index 3

rust_core