list_utilities
A collection of basic extension methods for Iterables, Lists, and Sets; and a library containing a base class for higher-level implementations of List.
See: num_utilities
Usage
import 'package:list_utilities/list_utilities.dart';
Iterable Methods
Methods extending Iterable are also be available on Lists, Sets, or any other implementation of Iterable.
random
The random method returns a random value from the iterable.
final numbers = [0, 1, 2, 3, 4];
print(numbers.random()); // 3 (or any of the other numbers.)
matches
The matches method returns true if the other iterable is the same length
as the calling iterable and contains all of the same elements.
matches has an optional parameter, ordered, which if true, requires the
elements of each iterable to be in the same order to satisfy matches.
final numbersA = {1, 2, 3, 4, 5};
final numbersB = {5, 4, 3, 2, 1};
print(numbersA.matches(numbersB)); // true
print(numbersA.matches(numbersB, ordered: true)); // false
List Methods
getRandom
The getRandom method returns a new set containing random
elements from the set.
final numbers = [0, 1, 2, 3, 4];
print(numbers.getRandom(3)); // [3, 1, 4] (or any other combination of numbers.)
removeRandom
The removeRandom method removes and returns an element from
the list at random.
final numbers = [0, 1, 2, 3, 4];
print(numbers.removeRandom()); // 3 (or any of the other numbers.)
print(numbers); // [0, 1, 2, 4]
Note: removeRandom is included on Lists and Sets, but not
Iterables because Iterables lack methods to remove elements without
first converting it to a List or Set.
removeNull
The removeNull method removes all null values from the list.
final numbers = [0, 1, null, 3, null];
numbers.removeNull();
print(numbers); // [0, 1, 3]
removeFirst
The removeFirst method removes the first item from the list.
final numbers = [0, 1, 2, 3, 4];
print(numbers.removeFirst()); // 0
print(numbers); // [1, 2, 3, 4]
removeFirstWhere
The removeFirstWhere method iterates through the list and removes
the first element that satisfies the test.
final numbers = [0, 1, 2, 3, 4];
numbers.removeFirstWhere((number) => number.isOdd);
print(numbers); // [0, 2, 3, 4]
removeLastWhere
The removeLastWhere method iterates through the list in reverse and
removes the first element that satisfies the test.
final numbers = [0, 1, 2, 3, 4];
numbers.removeLastWhere((number) => number.isOdd);
print(numbers); // [0, 1, 2, 4]
pluck
The pluck method removes and returns a subset of the elements
in the list from the element at start to the element at end,
or the end of the list if end is null.
final numbers = <int>[0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
print(numbers.pluck(3, 8)); // [3, 4, 5, 6, 7]
print(numbers); // [0, 1, 2, 8, 9]
resizeAndFill
The resizeAndFill method adds or removes elements from the list,
setting any new values to the provided value.
final numbers = [0, 1, 2, 3, 4];
numbers.resizeAndFill(-2, 0);
print(numbers); // [0, 1, 2]
numbers.resizeAndFill(2, 0);
print(numbers); // [0, 1, 2, 0, 0]
resizeAndGenerate
The resizeAndGenerate method adds or removes elements from the list,
setting any new values with the provided generator.
final numbers = [0, 1, 2, 3, 4];
numbers.resizeAndGenerate(5, (index) => index);
print(numbers); // [0, 1, 2, 3, 4, 0, 1, 2, 3, 4]
numbers.resizeAndGenerate(-5, (index) => index);
print(numbers); // [0, 1, 2, 3, 4]
removeFrom
The removeFrom method removes the specified number of elements,
starting at the provided index.
final numbers = [0, 1, 2, 3, 4];
numbers.removeFrom(3, 2);
print(numbers); // [0, 1, 2]
numbers.removeFrom(0, 2);
print(numbers); // [2]
removeFromEnd
The removeFromEnd method removes the specified number of elements
from the end of the list.
final numbers = [0, 1, 2, 3, 4];
numbers.removeFromEnd(2);
print(numbers); // [0, 1, 2]
transform
The transform method updates the element at the provided index to
the value returned by the provided transformer.
final numbers = [0, 1, 2, 3, 4];
numbers.transform(2, (number) => number * 2);
print(numbers); // [0, 1, 4, 3, 4]
transformAll
The transformAll method updates every element in a list to
the value returned by the provided transformer.
final numbers = [0, 1, 2, 3, 4];
numbers.transformAll((number) => number * 2);
print(numbers); // [0, 2, 4, 6, 8]
count
The count method returns the number of instances there are of the
provided object in a list.
final numbers = [0, 0, 1, 2, 1, 0, 0];
print(numbers.count(0)); // 4
print(numbers.count(1)); // 2
print(numbers.count(2)); // 1
Set Methods
getRandom
The getRandom method returns a new set containing random
elements from the set.
final numbers = {0, 1, 2, 3, 4};
print(numbers.getRandom(3)); // {3, 1, 4} (or any other combination of numbers.)
removeRandom
The removeRandom method removes and returns an element from
the set at random.
final numbers = {0, 1, 2, 3, 4};
print(numbers.removeRandom()); // 3 (or any of the other numbers.)
print(numbers); // {0, 1, 2, 4}
Note: removeRandom is included on Lists and Sets, but not Iterables
because Iterables lack methods to remove elements without first converting it
to a List or Set.
removeFirst
The removeFirst method removes the first element in the set and
returns the removed element.
final numbers = {0, 1, 2, 3, 4};
print(numbers.removeFirst()); // 0
print(numbers); // {1, 2, 3, 4}
removeLast
The removeLast method removes the last element in the set and
returns the removed element.
final numbers = {0, 1, 2, 3, 4};
print(numbers.removeLast()); // 4
print(numbers); // {0, 1, 2, 3}
removeRange
The removeRange method removes a range of elements from the set.
Note: This method should not be used on unordered sets, such as a HashSet.
final numbers = <int>{0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
numbers.removeRange(3, 8);
print(numbers); // {0, 1, 2, 8, 9}
pluck
The pluck method removes and returns a subset of the elements
in the set from the element at start to the element at end,
or the end of the list if end is null.
Note: This method should not be used on unordered sets, such as a HashSet.
final numbers = <int>{0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
print(numbers.pluck(3, 8)); // {3, 4, 5, 6, 7}
print(numbers); // {0, 1, 2, 8, 9}
+ operator
The + operator returns a new Set by appending the second Set's
values to the end of the first Sets'.
final numbersA = {1, 2, 3};
final numbersB = {4, 5, 6};
print(numbersA + numbersB); // {1, 2, 3, 4, 5, 6}
base_list
import 'package:list_utilities/base_list.dart';
The base_list library exposes an abstract class, BaseList, as well as a
number of typedefs to use when overriding methods in an implementing class.
BaseList implements List<E> and wraps another List<E>, elements, that
BaseList's methods interface with.
BaseList is intended to be used in cases where you need to implement a new type of list, but not every method necessary to implement a list needs to be customized.
Unlike List, BaseList requires growable as a parameter; which, depending
on the implementation, doesn't necessarily equate to the wrapped list, elements,
being a fixed-length list or not.
Note: Overridden methods that modify the length of elements should respect
growable, and throw an UnsupportedError if the user tries to modify the length
of the list, regardless of whether elements is a fixed-length list or not.
/// An implementation of `List<E>` that stores a list
/// containing every element added to it, even if those
/// elements have since been removed.
class HistoryList<E> extends BaseList<E> {
const HistoryList() : super(<E>[], growable: true);
List<E> get history => List<E>.from(_history);
final _history = <E>[];
@override
void add(E value) {
elements.add(value);
_history.add(value);
}
@override
void addAll(Iterable<E> iterable) {
elements.addAll(iterable);
_history.addAll(iterable);
}
@override
void insert(int index, E element) {
elements.insert(index, element);
_history.add(element);
}
@override
void insertAll(int index, Iterable<E> iterable) {
elements.insertAll(index, iterable);
_history.addAll(iterable);
}
}
See: labeled_list and unique_list for complete examples of how BaseList should be implemented.