Returns an array containing the non-nil results of calling the given transformation with each element of this sequence.
SDK
- Xcode 11.0+
Framework
- Swift Standard Library
Declaration
func compactMap<ElementOfResult>(_ transform: (CollectionDifference <ChangeElement>.Change) throws -> ElementOfResult?) rethrows -> [ElementOfResult]
Parameters
transformA 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 compact 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.