How can I remove or replace all punctuation characters from a String?

Question

I have a string composed of words, some of which contain punctuation, which I would like to remove, but I have been unable to figure out how to do this.

For example if I

Answer 1

This works with Xcode 8.1, Swift 3:

First define general-purpose extension for filtering by CharacterSet:

extension String {
  func removingCharacters(inCharacterSet forbiddenCharacters:CharacterSet) -> String 
{
    var filteredString = self
    while true {
      if let forbiddenCharRange = filteredString.rangeOfCharacter(from: forbiddenCharacters)  {
        filteredString.removeSubrange(forbiddenCharRange)
      }
      else {
        break
      }
    }

    return filteredString
  }
}

Then filter using punctuation:

let s:String = "Hello, world!"
s.removingCharacters(inCharacterSet: CharacterSet.punctuationCharacters) // => "Hello world"