Variables and functions

Extensions can contain functions and computed/constant get variables. They are in the format

extension ExtensionOf {
    //new functions and get-variables
}

To reference the instance of the extended object, self can be used, just as it could be used

To create an extension of String that adds a .length() function which returns the length of the string, for example

extension String {
    func length() -> Int {
        return self.characters.count
    }
}

"Hello, World!".length() // 13

Extensions can also contain get variables. For example, adding a .length variable to the string which returns the length of the string

extension String {
    var length: Int {
        get {
            return self.characters.count
        }
    }
}

"Hello, World!".length // 13