swift类型嵌套

/**

1.类型嵌套实例

2.类型嵌套引用

枚举类型常被用于实现特定类或结构体的功能。也能够在有多种变量类型的环境中，方便地定义通用类或结构体来使用，为了实现这种功能，swift允许你定义类型嵌套，可以在枚举类型、类和结构体中定义支持嵌套类型

要在一个类型中嵌套另一个类型，将需要嵌套的类型的定义写在被嵌套类型的区域{}内，而且可以根据需要定义多级嵌套

*/

//类型嵌套实例

struct BlackjackCard {

//嵌套定义枚举型Suit

enum Suit: Character {

case Spades =
"♠︎", Hearts =
"♡", Diamonds = "♢", Clubs =
"♣︎";

}

//嵌套定义枚举类型Rank

enum Rank: Int {

case Two =
2, Three, Four, Five, Six, Seven, Eight, Nine, Ten;

case Jack, Queen, King, Ace;

struct Values {

let first:
Int, second: Int?;

}

var values:
Values {

switch
self {

case .Ace:

return
Values(first: 1, second:
11);

case .Jack, .Queen, .King:

return
Values(first: 10, second:
nil);

default:

return
Values(first: self.rawValue, second:
nil);

}

}

}

//BlackjackCard的属性和方法

let rank: Rank, suit:
Suit;

var description:
String {

var output =
"suit is \(suit.rawValue)";

output += " value is \(rank.values.first) ";

if let second =
rank.values.second {

output += "or \(second) ";

}

return output;

}

}

let theAceOfSpades =
BlackjackCard(rank: .Ace, suit: .Spades);

print("theAceOfSpades:
\(theAceOfSpades.description)");

//类型嵌套的引用

/**

在外部对嵌套类型的引用，以被嵌套类型的名字为前缀，加上索要引用的属性名

*/

let heartsSymbol =
BlackjackCard.Suit.Hearts.rawValue;

print(heartsSymbol);