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简介
在Scala中并没有枚举类型,但在标准类库中提供了Enumeration类来产出枚举。扩展Enumeration类后,调用Value方法来初始化枚举中的可能值。
内部类Value实际上是一个抽象类,真正创建的是Val。因为实际上是Val,所以可以为Value传入id和name
如果不指定,id就是在前一个枚举值id上加一,name则是字段名
scala枚举示例
object TrafficLightColor extends Enumeration {
type TrafficLightColor = Value
val Red = Value(0, "Stop")
val Yellow = Value(10)
val Green = Value("Go")
}
object Margin extends Enumeration {
type Margin = Value
val TOP, BOTTOM, LEFT, RIGHT = Value
}
import test.TrafficLightColor._
import test.Margin._
object Driver extends App {
println(BOTTOM, BOTTOM.id)
def doWhat(color: TrafficLightColor) = {
if (color == Red) "stop"
else if (color == Yellow) "hurry up" else "go"
}
//使用match匹配
def doWhat2(color: TrafficLightColor) = color match {
case Red => "stop"
case Yellow => "hurry up"
case _ => "go"
}
// load Red
val red = TrafficLightColor(0) // Calls Enumeration.apply
println(red, red.id)
println(doWhat(red))
println(doWhat2(TrafficLightColor.Yellow))
//打印出所有枚举
Margin.values.foreach { v => println(v,v.id)}
}
来源:oschina
链接:https://my.oschina.net/u/1410765/blog/490061