indices(where:)

Declaration

func indices(where predicate: (Self.Element) throws -> Bool) rethrows -> RangeSet<Self.Index>

Parameters

• predicate:

  A closure that takes an element as its argument and returns a Boolean value that indicates whether the passed element represents a match.

Return Value

A set of the indices of the elements for which predicate returns true.

Discussion

For example, you can use this method to find all the places that a vowel occurs in a string.

let str = "Fresh cheese in a breeze"
let vowels: Set<Character> = ["a", "e", "i", "o", "u"]
let allTheVowels = str.indices(where: { vowels.contains($0) })
// str[allTheVowels].count == 9