Hands-On Design Patterns with Swift

The public wrapper

Now that we have all of the components required to implement our public wrapper, let's have a look at what's left to do:

• Implement an initializer that takes Animal<F>
• Box Animal<F> into _AnyAnimalBox<A>
• Store the boxed animal as _AnyAnimalBase<F> (remember, we can't use A as a generic type, but we can use F)
• Forward all calls to from the public wrapper to the box:

final class AnyAnimal<T>: Animal where T: Food {    typealias FoodType = T    private let box: _AnyAnimalBase<T>    init<A: Animal>(_ animal: A) where A.FoodType == T {        box = _AnyAnimalBox(animal)    }    // Call forwarding for implementing Animal    var preferredFood: T? {        get { return box.preferredFood }        set { box.preferredFood = newValue }    }        var name: String { return box.name ...