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]

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}

+ 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.