Generic Instance Method

compactMap(_:)

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

Declaration

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

Parameters

transform

A closure that accepts an element of this sequence as its argument and returns an optional value.

Return Value

An array of the non-nil results of calling transform with each element of the sequence.

Discussion

Use this method to receive an array of non-optional values when your transformation produces an optional value.

In this example, note the difference in the result of using map and compactMap with a transformation that returns an optional Int value.

let possibleNumbers = ["1", "2", "three", "///4///", "5"]

let mapped: [Int?] = possibleNumbers.map { str in Int(str) }
// [1, 2, nil, nil, 5]

let compactMapped: [Int] = possibleNumbers.compactMap { str in Int(str) }
// [1, 2, 5]

Complexity: O(m + n), where n is the length of this sequence and m is the length of the result.

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 map<T>(((key: Key, value: Value)) -> T) -> [T]

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

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 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.