在 Java 中你可以：
public enum Enum {
ONE {
public String method() {
return "1";
}
},
TWO {
public String method() {
return "2";
}
},
THREE {
public String method() {
return "3";
}
};
public abstract String method();
}
在 Scala 中如何做到这一点？
编辑/有用的链接：
- https://github.com/rbricks/itemized https://github.com/rbricks/itemized
- http://pedrorijo.com/blog/scala-enums/ http://pedrorijo.com/blog/scala-enums/
下面是通过扩展 Enumeration.Val 类向 scala 枚举添加属性的示例。
object Planet extends Enumeration {
protected case class Val(val mass: Double, val radius: Double) extends super.Val {
def surfaceGravity: Double = Planet.G * mass / (radius * radius)
def surfaceWeight(otherMass: Double): Double = otherMass * surfaceGravity
}
implicit def valueToPlanetVal(x: Value) = x.asInstanceOf[Val]
val G: Double = 6.67300E-11
val Mercury = Val(3.303e+23, 2.4397e6)
val Venus = Val(4.869e+24, 6.0518e6)
val Earth = Val(5.976e+24, 6.37814e6)
val Mars = Val(6.421e+23, 3.3972e6)
val Jupiter = Val(1.9e+27, 7.1492e7)
val Saturn = Val(5.688e+26, 6.0268e7)
val Uranus = Val(8.686e+25, 2.5559e7)
val Neptune = Val(1.024e+26, 2.4746e7)
}
scala> Planet.values.filter(_.radius > 7.0e6)
res16: Planet.ValueSet = Planet.ValueSet(Jupiter, Saturn, Uranus, Neptune)
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