Reification example

reify.swift

protocol InitProtocol { init() }

struct SomeStruct<T: InitProtocol> {
    var x: T? = nil
    mutating func instantiate() {
        if x == nil {
            x = T()
        }
    }
}

struct Foo : InitProtocol {
    func favoriteString() -> String {
        return "reify me please"
    }
}

struct Bar : InitProtocol {
    func favoriteString() -> String {
        return "another string"
    }
}

var a = SomeStruct<Foo>()
var b = SomeStruct<Bar>()
a.instantiate()
b.instantiate()
(a.x?.favoriteString())!    // prints out "reify me please"
(b.x?.favoriteString())!    // prints out "another string"