Swift学习笔记，10--枚举

1.定义语法:

enum SomeEnumeration {
  // enumeration definition goes here
}

2.使用

enum CompassPoint {
    case North
    case South
    case East
    case West
}

var directionToHead = CompassPoint.West

directionToHead = .South
switch directionToHead {
case .North:
    println("Lots of planets have a north")
case .South:
    println("Watch out for penguins")
case .East:
    println("Where the sun rises")
default:
    println("Nothing")
}

　　注：1.变量一个次赋值为枚举类型以后，第二次赋值可以使用点语法省略,即.South

　　　　2.switch中必须覆盖所有的枚举类型,如果太多,可使用default

3.相关值（Associated Values）

swift语句中可以储存任何类型的相关值

enum Chazidian {
    case Pianpang(String, String)
    case Zimu(String)
    case Bihua(Int)
}

var c1 = Chazidian.Pianpang("一","田")
var c2 = Chazidian.Zimu("a")
var c3 = Chazidian.Bihua(3)

switch c3 {
case .Pianpang(let s1, let s2):
    println("偏旁:\(s1),\(s2)")
case .Zimu(let s3):
    println("字母:\(s3)")
case .Bihua(let s4):
    println("笔画:\(s4)")
}   //笔画:3

3.默认值

swift中枚举的默认值需要自己手动添加:

//方式1:对每一个做赋值
enum ASCIIControlCharacter: Character {
    case Tab = "\t"
    case LineFeed = "\n"
    case CarriageReturn = "\r"
}

//方式2:自动递增
enum Planet: Int {
    case Mercury = 1, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune
}