let myString = "5"
let sum = 3 +  Int(myString)!  // Produces 8
print(Int(myString)!)

let str = "My test String Index"
let index = str.index(str.startIndex, offsetBy: 4)
str[index] // Returns e from test

let endIndex = str.index(str.endIndex, offsetBy:-2)
str[Range(index ..< endIndex)] // returns String "est String Ind"

str.substring(from: index) // returns String "est String Index"
str.substring(to: index) // returns String "My t"

let string = "1"
if let integer = Int(string) {
    print(integer)
}