An extension of the Swift String type to provide kebab case formatting.

String+KebabCase.swift

/// An extension to format strings in *kebab case*.
extension String {
  
    /// A collection of all the words in the string by separating out any punctuation and spaces.
    var words: [String] {
        return components(separatedBy: CharacterSet.alphanumerics.inverted).filter { !$0.isEmpty }
    }

    /// Returns a lowercased copy of the string with punctuation removed and spaces replaced
    /// by a single hyphen, e.g., "the-quick-brown-fox-jumps-over-the-lazy-dog".
    ///
    /// *Lower kebab case* (or, illustratively, *kebab-case*) is also known as *spinal case*,
    /// *param case*, *Lisp case*, and *dash case*.
    func lowerKebabCased() -> String {
        return self.words.map({ $0.lowercased() }).joined(separator: "-")
    }

    /// Returns an uppercased copy of the string with punctuation removed and spaces replaced
    /// by a single hyphen, e.g., "THE-QUICK-BROWN-FOX-JUMPS-OVER-THE-LAZY-DOG".
    ///
    /// *Upper kebab case* (or, illustratively, *KEBAB-CASE*) is also known as *train case*.
    func upperKebabCased() -> String {
        return self.words.map({ $0.uppercased() }).joined(separator: "-")
    }

    /// Returns a copy of the string with punctuation removed and spaces replaced by a single
    /// hyphen, e.g., "The-quick-brown-fox-jumps-over-the-lazy-dog". Upper and lower casing
    /// is maintained from the original string.
    func mixedKebabCased() -> String {
        return self.words.joined(separator: "-")
    }

}