struct Candies {
    let candies: [String]
}

extension Candies: Sequence {
    func makeIterator() -> CandiesIterator {
        return CandiesIterator(sequence: candies, current: 0)
    }
}

struct CandiesIterator: IteratorProtocol {

    let sequence: [String]
    var current = 0

    mutating func next() -> String? {
        defer { current += 1 }
        return sequence.count > current ? sequence[current] : nil
    }
}

struct Whatevers<T> {
    let whatevers: [T]
}

extension Whatevers: Sequence {
    func makeIterator() -> Whatevers<T>.Iterator {
        return WhateversIterator(sequence: whatevers, current: 0)
    }
}


struct WhateversIterator<T>: IteratorProtocol {
    let sequence: [T]
    var current = 0

    mutating func next() -> WhateversIterator.Element? {
        defer { current += 1 }
        return sequence.count > current ? sequence[current] : nil
    }
}