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

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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);

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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"]);

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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));

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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));