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: ((offset: Int, element: Base.Element)) 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.