Learning Swift™ Programming

Protocols in Collections

Protocols can be used as types, so it shouldn’t be a surprise that a protocol can also be used as the type of a collection. Think about the case of the Walkable class from the previous section. Say that you want to create something else that can walk, such as a dog. Here’s what you do:

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class Dog:Walkable {    var name = "Penny"    func walk(#numOfSteps:Int) {        println("The dog is walking \(numOfSteps) steps")    }}let dog = Dog()let human = Human()var walkers = [Walkable]()walkers.append(dog)walkers.append(human)for walker in walkers {    walker.walk(numOfSteps:10)}

Here you have a Dog and a Human, and they are both Walkable. You also have an array that is strictly typed for anything ...