I get the same bug

var letters = currentGame.formattedWord.map { String($0) } Another way of writing that is var letters = currentGame.formattedWord.map { letter in return String(letter) } We're essentially taking each character ('letter') from formattedWord and initializing a String from that letter using String(letter) and by using the closure on map, we're creating a whole new String array that gets passed into letters. The first solution is just a short-hand syntax for the second one. I recommend looking into closures and array operations.