Generic Instance Method

map(_:)

Returns an array containing the results of mapping the given closure over the sequence’s elements.

Declaration

func map<T>(_ transform: ((key: Key, value: Value)) throws -> T) rethrows -> [T]

Parameters

transform

A mapping closure. transform accepts an element of this sequence as its parameter and returns a transformed value of the same or of a different type.

Return Value

An array containing the transformed elements of this sequence.

Discussion

In this example, map is used first to convert the names in the array to lowercase strings and then to count their characters.

let cast = ["Vivien", "Marlon", "Kim", "Karl"]
let lowercaseNames = cast.map { $0.lowercased() }
// 'lowercaseNames' == ["vivien", "marlon", "kim", "karl"]
let letterCounts = cast.map { $0.count }
// 'letterCounts' == [6, 6, 3, 4]

See Also

Transforming a Dictionary

func mapValues<T>((Value) -> T) -> Dictionary<Key, T>

Returns a new dictionary containing the keys of this dictionary with the values transformed by the given closure.

func reduce<Result>(Result, (Result, (key: Key, value: Value)) -> Result) -> Result

Returns the result of combining the elements of the sequence using the given closure.

func reduce<Result>(into: Result, (inout Result, (key: Key, value: Value)) -> ()) -> Result

Returns the result of combining the elements of the sequence using the given closure.

func compactMap<ElementOfResult>(((key: Key, value: Value)) -> ElementOfResult?) -> [ElementOfResult]

Returns an array containing the non-nil results of calling the given transformation with each element of this sequence.

func compactMapValues<T>((Value) -> T?) -> Dictionary<Key, T>

Returns a new dictionary containing only the key-value pairs that have non-nil values as the result of transformation by the given closure.

func flatMap<SegmentOfResult>(((key: Key, value: Value)) -> SegmentOfResult) -> [SegmentOfResult.Element]

Returns an array containing the concatenated results of calling the given transformation with each element of this sequence.

func flatMap<ElementOfResult>(((key: Key, value: Value)) -> ElementOfResult?) -> [ElementOfResult]Deprecated
func sorted(by: ((key: Key, value: Value), (key: Key, value: Value)) -> Bool) -> [(key: Key, value: Value)]

Returns the elements of the sequence, sorted using the given predicate as the comparison between elements.

func shuffled() -> [(key: Key, value: Value)]

Returns the elements of the sequence, shuffled.

func shuffled<T>(using: inout T) -> [(key: Key, value: Value)]

Returns the elements of the sequence, shuffled using the given generator as a source for randomness.