KTX

The KTX Library provides a comprehensive set of tools for managing collections – groups of a variable number of items (possibly zero) that share significance to the problem being solved and are operated upon commonly.

Getting Started

associateBy
mapToList
sortBy
groupBy
mapIndexed
zip
let

associateBy

associateBy is an operation allows associate the list items with the given key.

final List<Fruit> fruits = [
    Fruit(id: 1, kind: "Pear", color: "Red"),
    Fruit(id: 2, kind: "Apple", color: "Green")
];
final Map<int, Fruit> mappedFruits = fruits
    .associateBy((fruit) => fruit.id);

mapToList

mapToList returns a list containing the results of applying the given transform function.

final Map<int, Fruit> fruits = {
  1: Fruit(kind: "Pear", color: "Red"),
  2: Fruit(kind: "Apple", color: "Green")
};
final List<String> fruitNames = fruits
    .mapToList((key, fruit) => fruit.kind);

sortBy

sortBy sorts elements in the list in-place according to natural sort order of the value returned by specified selector function.

final List<Fruit> fruits = [
    Fruit(id: 1, kind: "Apple", color: "Red"),
    Fruit(id: 2, kind: "Apple", color: "Green")
];
final List<Fruit> sortedByNamefruits = fruits
    .sortBy((fruit) => fruit.kind);

groupBy

groupBy groups elements of the original collection by the key returned by the given keySelector function applied to each element and returns a map where each group key is associated with a list of corresponding elements.

final List<Fruit> fruits = [
    Fruit(id: 1, kind: "Apple", color: "Red"),
    Fruit(id: 2, kind: "Apple", color: "Green")
];
final Map<String, List<Fruit>> groupedFruits = fruits
    .groupBy((fruit) => fruit.kind);

mapIndexed

mapIndexed returns a list containing the results of applying the given transform function to each element and its index in the original collection.

final fruits = ["Apple", "Pear", "Orange"];
final indexedFruits = fruits.mapIndexed((index, fruit) => "${index + 1}: $fruit");

/// ["1: Apple", "2: Pear", "3: Orange"]);

zip

zip returns a list of values built from the elements of this collection and the other collection with the same index.

final kinds = ["Apple", "Pear", "Apricot"];
final colors = ["Red", "Green", "Orange"];
final fruits = kinds.zip(colors, (kind, color) => Fruit(kind, color));

let

let calls the specified function block with this value as its argument and returns its result.

final Fruit? fruit = Fruit(id: 1, kind: "Apple", color: "Red");
fruit?.let((fruit) => print(fruit));

KTX