Learning Swift™ Programming

Back to Optional Protocol Requisites

With optional chaining tools in hand, you can now test to see whether your methods exist:

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@objc protocol Bearable {    func growl()    optional func cough() -> String //Apparently bears cough when they are scared.}@objc class Bear:Bearable {    var name = "Black Bear"    func growl() {        println("Growllll!!!")    }}@objc class Forest {    var bear:Bearable?    func scareBears() {        if let cough = bear?.cough?() {            println(cough)        } else {            println("bear was scared")        }    }}var forest = Forest()forest.scareBears()

You check whether the Bearable implementation exists with optional chaining. You assign the return of the method with optional ...