Finding out whether a string is numeric or not

Question

How can we check if a string is made up of numbers only. I am taking out a substring from a string and want to check if it is a numeric substring or not.

NSS         


        

Answer 1

For Swift 3

var onlyDigits: CharacterSet = CharacterSet.decimalDigits.inverted
if testString.rangeOfCharacter(from: onlyDigits) == nil {
  // String only consist digits 0-9
}