Class Enumeration.Enumeration

abstract class Enumeration(initial: Int) extends Serializable

Defines a finite set of values specific to the enumeration. Typically these values enumerate all possible forms something can take and provide a lightweight alternative to case classes.

Each call to a Value method adds a new unique value to the enumeration. To be accessible, these values are usually defined as val members of the enumeration.

All values in an enumeration share a common, unique type defined as the Value type member of the enumeration (Value selected on the stable identifier path of the enumeration instance).

Values SHOULD NOT be added to an enumeration after its construction; doing so makes the enumeration thread-unsafe. If values are added to an enumeration from multiple threads (in a non-synchronized fashion) after construction, the behavior of the enumeration is undefined.

// Define a new enumeration with a type alias and work with the full set of enumerated values
object WeekDay extends Enumeration {
 type WeekDay = Value
 val Mon, Tue, Wed, Thu, Fri, Sat, Sun = Value
}
import WeekDay._
def isWorkingDay(d: WeekDay) = ! (d == Sat || d == Sun)
WeekDay.values filter isWorkingDay foreach println
// output:
// Mon
// Tue
// Wed
// Thu
// Fri

// Example of adding attributes to an enumeration by extending the Enumeration.Val class
object Planet extends Enumeration {
 protected case class PlanetVal(mass: Double, radius: Double) extends super.Val {
   def surfaceGravity: Double = Planet.G * mass / (radius * radius)
   def surfaceWeight(otherMass: Double): Double = otherMass * surfaceGravity
 }
 import scala.language.implicitConversions
 implicit def valueToPlanetVal(x: Value): PlanetVal = x.asInstanceOf[PlanetVal]
 val G: Double = 6.67300E-11
 val Mercury = PlanetVal(3.303e+23, 2.4397e6)
 val Venus   = PlanetVal(4.869e+24, 6.0518e6)
 val Earth   = PlanetVal(5.976e+24, 6.37814e6)
 val Mars    = PlanetVal(6.421e+23, 3.3972e6)
 val Jupiter = PlanetVal(1.9e+27, 7.1492e7)
 val Saturn  = PlanetVal(5.688e+26, 6.0268e7)
 val Uranus  = PlanetVal(8.686e+25, 2.5559e7)
 val Neptune = PlanetVal(1.024e+26, 2.4746e7)
}
println(Planet.values.filter(_.radius > 7.0e6))
// output:
// Planet.ValueSet(Jupiter, Saturn, Uranus, Neptune)

Classlikes

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protected class Val(i: Int, name: String) extends Value with Serializable

A class implementing the scala.Enumeration.Value type. This class can be overridden to change the enumeration's naming and integer identification behaviour.

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abstract class Value extends Ordered[Value] with Serializable

The type of the enumerated values.

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object ValueOrdering extends Ordering[Value]

An ordering by id for values of this set

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class ValueSet extends AbstractSet[Value] with SortedSet[Value] with SortedSetOps[Value, SortedSet, ValueSet] with StrictOptimizedIterableOps[Value, Set, ValueSet] with Serializable

A class for sets of values. Iterating through this set will yield values in increasing order of their ids.

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object ValueSet extends SpecificIterableFactory[Value, ValueSet]

A factory object for value sets

Constructors

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def this()

Concrete methods

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final protected def Value: Value

Creates a fresh value, part of this enumeration.

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final protected def Value(i: Int): Value

Creates a fresh value, part of this enumeration, identified by the integer i.

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final protected def Value(name: String): Value

Creates a fresh value, part of this enumeration, called name.

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final protected def Value(i: Int, name: String): Value

Creates a fresh value, part of this enumeration, called name and identified by the integer i.

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final def apply(x: Int): Value

The value of this enumeration with given id x

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final def maxId: Int

The one higher than the highest integer amongst those used to identify values in this enumeration.

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protected def readResolve(): AnyRef

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override def toString: String

The name of this enumeration.

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def values: ValueSet

The values of this enumeration as a set.

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final def withName(s: String): Value

Return a Value from this Enumeration whose name matches the argument s. The names are determined automatically via reflection.

Concrete fields

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protected var nextId: Int

The integer to use to identify the next created value.

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protected var nextName: Iterator[String]

The string to use to name the next created value.