enum Media {
  case Book(title: String, author: String, year: Int)
  case Movie(title: String, director: String, year: Int)
  case WebSite(urlString: String)
}

let mediaList: [Media] = [
  .Book(title: "Harry Potter and the Philosopher's Stone", author: "J.K. Rowling", year: 1997),
  .Movie(title: "Harry Potter and the Philosopher's Stone", director: "Chris Columbus", year: 2001),
  .Book(title: "Harry Potter and the Chamber of Secrets", author: "J.K. Rowling", year: 1999),
  .Movie(title: "Harry Potter and the Chamber of Secrets", director: "Chris Columbus", year: 2002),
  .Book(title: "Harry Potter and the Prisoner of Azkaban", author: "J.K. Rowling", year: 1999),
  .Movie(title: "Harry Potter and the Prisoner of Azkaban", director: "Alfonso Cuarón", year: 2004),
  .WebSite(urlString: "https://en.wikipedia.org/wiki/List_of_Harry_Potter-related_topics")
]

extension Media {
  var title: String? {
    switch self {
    case let .Book(title, _, _): return title
    case let .Movie(title, _, _): return title
    default: return nil
    }
  }
  var kind: String {
    // Remember part 1 where we bind all the associated values in one single anonymous tuple `_`?
    switch self {
    case .Book(_): return "Book"
    case .Movie(_): return "Movie"
    case .WebSite(_): return "Web Site"
    }
  }
}

print("All mediums with a title starting with 'Harry Potter'")
for case let (title?, kind) in mediaList.map({ ($0.title, $0.kind) })
  where title.hasPrefix("Harry Potter") {
    print(" - [\(kind)] \(title)")
}