swift的泛型貌似还差点意思

protocol Container {

    typealias ItemType

    mutating func append(item: ItemType)

    mutating func removelast() -> ItemType

    var count: Int {get}

    subscript(i: Int) -> ItemType{get}

}
// Container<T> ???

// protocol not gen!

struct Hole<T>: Container {

    typealias ItemType = T

    var elements = ItemType[]()

    var count: Int {

    get{

        return elements.count

    }

    }

    mutating func append(item: ItemType){

        elements.append(item)

    }

    subscript(i: Int) -> ItemType {

        return elements[i]

    }

    mutating func removelast() -> ItemType{

        return elements.removeLast()

    }

}
class Stack<T>{

    var storage = Hole<T>()

    typealias ItemType = T

    typealias StorageType = Hole<T>.ItemType

    func push(item:ItemType) {

        storage.append(item)

    }

    func pop() -> ItemType{

        return storage.removelast()

    }

}

protocol不支持泛型,带来很多限制,不够灵活, 难道是为了兼容objc?

如果可以这么用,就会更灵活

class Stack<T, T2:Container>{

    var storage = T2<T>()

    ....

}