枚举

　　使用enum创建枚举——注意 Swift 的枚举可以关联方法：

1 enum Rank: Int { 2     case Ace = 1 case Two, Three, Four, Five, Six, Seven, Eight, Nine, Ten 3     case Jack, Queen, King 4         func simpleDescription () -> String { 5         switch self { 6             case .Ace: 7                 return "ace" case .Jack: 8                 return "jack" case .Queen: 9                 return "queen" case .King:10                 return "king" default:11                 return String (self.toRaw ())12         }13     }14 }15 let ace = Rank.Ace16 let aceRawValue = ace.toRaw ()

使用toRaw和fromRaw在原始（raw）数值和枚举值之间进行转换：

1 if let convertedRank = Rank.fromRaw (3) {2     let threeDescription = convertedRank.simpleDescription ()3 }

注意枚举中的成员值（member value）是实际的值（actual value），和原始值（raw value）没有必然关联。

　　一些情况下枚举不存在有意义的原始值，这时可以直接忽略原始值：

1 enum Suit { 2     case Spades, Hearts, Diamonds, Clubs 3         func simpleDescription () -> String { 4         switch self { 5             case .Spades: 6                 return "spades" case .Hearts: 7                 return "hearts" case .Diamonds: 8                 return "diamonds" case .Clubs: 9                 return "clubs"10         }11     }12 }13 let hearts = Suit.Hearts14 let heartsDescription = hearts.simpleDescription ()

除了可以关联方法，枚举还支持在其成员上关联值，同一枚举的不同成员可以有不同的关联的值：

1 enum ServerResponse { 2     case Result (String, String) 3     case Error (String) 4 } 5  6 let success = ServerResponse.Result ("6:00 am", "8:09 pm") 7 let failure = ServerResponse.Error ("Out of cheese.") 8  9 switch success {10     case let .Result (sunrise, sunset):11         let serverResponse = "Sunrise is at \(sunrise) and sunset is at \(sunset)." case let .Error (error):12         let serverResponse = "Failure... \(error)"13 }

 

结构

　　Swift 使用struct关键字创建结构。结构支持构造器和方法这些类的特性。结构和类的最大区别在于：结构的实例按值传递（passed by value），而类的实例按引用传递（passed by reference）。

1 struct Card {2     var rank: Rank3     var suit: Suit4     func simpleDescription () -> String {5         return "The \(rank.simpleDescription ()) of \(suit.simpleDescription ())"6     }7 }8 let threeOfSpades = Card (rank: .Three, suit: .Spades)9 let threeOfSpadesDescription = threeOfSpades.simpleDescription ()