You need to map the Character
array back to String
let resultsArray = lettersarray.dropLast(lettersarray.count - targetNum).map{String($0)}
alternatively (credits to Leo Dabus)
let letters = "abcdefghijklmnopqrstuvwxyz"
let targetNum = 14
let resultsArray = letters.characters.prefix(targetNum).map{String($0)}
4
solved How to return an subset of Array of characters?