Swift 枚举使用

枚举

enum Media {
    case Book(title: String, author: String, year: Int)
    case Movie(title: String, director: String, year: Int)
    case WebSite(url: NSURL, title: String)
}
let book = Media.Book(title: "20,000 leagues under the sea", author: "Jules Verne", year: 1870)

extension Media {
    var mediaTitle: String {
        switch self {
        case .Book(title: let aTitle, author: _, year: _), let .Movie(aTitle, _, _):
            return aTitle
        case .WebSite(let url, let title):
            return title
        }
    }
}
book.mediaTitle

extension Media {
    var isFromJulesVerne: Bool {
        switch self {
        case .Book(title: _, author: "Jules Verne", year: _): return true
        case .Movie(title: _, director: "Jules Verne", year: _): return true
        default: return false
        }
    }
}
book.isFromJulesVerne

extension Media {
    func checkAuthor(author: String) -> Bool {
        switch self {
        case .Book(title: _, author: author, year: _): return true
        case .Movie(title: _, director: author, year: _): return true
        default: return false
        }
    }
}
book.checkAuthor(author: "Jules Verne")


if case let Media.Book(title, _, _) = book {
    print("This is a book named \(title)")
}
// guard case let Media.Book(_, _, year) = book else { ... }
// for case let Media.Book(_, _, year) in array { ... }
if case let Media.Book(_, _, year) = book, year > 2000 {
    print("This is a book year \(year)")
}
枚举

鸣谢
