1. About the
Scala EnumerationWhile enumerations are a built-in
part of many programming languages, Scala takes a different route
and implements them as a class in its standard library. This means
there is no special syntax for enumerations in Scala, as in Java
and C#. Instead, you just define an object that extends the
Enumeration class.
as it is quoted in the above text
1. There is no built-in construct for
enumeration in Scala language
2. Scala enumeration is just an object
3. the scala enumeration object extends from
"Enumeration"
4. There is no connection between Scala
enumerations and the enum
constructs in Java and C#.
2. Enumeration example I, longer form//
code-examples/Rounding/enumeration-script.scalapackage
ch03object Breed extends
Enumeration {
// 1.
Value is a method, take a string argument. This method assign a
long-form breed name to each enumeration value
val
doberman = Value("Doberman Pinscher")
val
yorkie = Value("Yorkshire Terrier")
val
scottie = Value("Scottish Terrier")
val dane
= Value("Great Dane")
val
portie = Value("Portuguese Water Dog")
}object EnumerationScript
{
// 2. Unit is the void in Scala
def main(args : Array[String]) : Unit = {
// 3. each enumeration has a unique id
// 4. Enumeration.values get value collection
for (breed
<- Breed.values) println(breed.id
+ "\t" + breed)
Breed.values.filter(_.toString.endsWith("Terrier")).foreach(println)
}
3. Enumeration example II, longer form
//
code-examples/Rounding/enumeration-script.scala
package
ch03object WeekDay extends
Enumeration {
// 1.
type alias
type
WeekDay = Value
// 2.
scala enumeratio are just normal object, use vals to indicated
different "enumeration" values
val Mon,
Tue, Wed, Thu, Fri, Sat, Sun = Value
}object DaysEnumerationScript
{
// 3.
import all enumerations, incluing the type alias
import
WeekDay._
def
isWorkingDay (d : WeekDay) = ! (d == Sat || d ==
Sun)
def
main(args : Array[String]) : Unit = {
WeekDay.values filter isWorkingDay foreach
println
}
