Get the last character of a string without using array?

Question

I have a string

let stringPlusString = TextBoxCal.text

I want to get the last character of stringPlusString. I do not want to

Answer 1

Swift 4:

First some char Last some char

let strOSName = "mac operating system"
print(strOSName.prefix(3))       //first char. o/p:  MAC
print(strOSName.suffix(6))       //last char.  o/p:  system