This is a fully type safe enumeration framework. It takes more setup & code than the built-in Scala Enumeration class,
but it will pay off in 2 major ways:
1. you get to decide what happens when a conversion from a string to enum value fails
2. you get compiler warnings when you miss a match on one or more enum values (ie: non-exhaustive match error)
these benefits are worth the relatively small bit of extra code per enumeration.
How to use this to create enumerations of your own:
1. create your enumeration:
package my.package
//you must include this to avoid extending build-in scala enumerations
import com.stackmob.common.enumeration._
//make sure this is sealed and an abstract class, not a trait
sealed abstract class MyEnum extends Enumeration
object MyEnumValue1 extends MyEnum {
override lazy val stringVal = "my_enum_value_1"
}
object MyEnumValue2 extends MyEnum {
override lazy val stringVal = "my_enum_value_2"
}
//create an EnumReader that knows how to convert strings into a MyEnum if the lowercase of the string
//matches the lowercase of the enum string value value
implicit val reader: EnumReader[MyEnum] = lowerEnumReader(MyEnumValue1, MyEnumValue2)
2. import your enum & the Enumeration implicits where you want to use the enum:
package my.package
import com.stackmob.common.enumeration._
3. use your enumeration & the implicits you imported to convert strings to your enum values:
"my_enum_value_1".readEnum[MyEnum] match {
case Some(MyEnumValue1) => doStuffForMyEnumValue1()
case Some(MyEnumValue2) => doStuffForMyEnumValue2()
//you will get warnings for non-exhaustive matches if you have more MyEnum subclasses than these
case None => doStuffForNoEnum()
}
This is a fully type safe enumeration framework. It takes more setup & code than the built-in Scala Enumeration class, but it will pay off in 2 major ways:
1. you get to decide what happens when a conversion from a string to enum value fails 2. you get compiler warnings when you miss a match on one or more enum values (ie: non-exhaustive match error)
these benefits are worth the relatively small bit of extra code per enumeration.
How to use this to create enumerations of your own:
1. create your enumeration:
package my.package //you must include this to avoid extending build-in scala enumerations import com.stackmob.common.enumeration._ //make sure this is sealed and an abstract class, not a trait sealed abstract class MyEnum extends Enumeration object MyEnumValue1 extends MyEnum { override lazy val stringVal = "my_enum_value_1" } object MyEnumValue2 extends MyEnum { override lazy val stringVal = "my_enum_value_2" } //create an EnumReader that knows how to convert strings into a MyEnum if the lowercase of the string //matches the lowercase of the enum string value value implicit val reader: EnumReader[MyEnum] = lowerEnumReader(MyEnumValue1, MyEnumValue2)2. import your enum & the Enumeration implicits where you want to use the enum:
package my.package import com.stackmob.common.enumeration._3. use your enumeration & the implicits you imported to convert strings to your enum values:
"my_enum_value_1".readEnum[MyEnum] match { case Some(MyEnumValue1) => doStuffForMyEnumValue1() case Some(MyEnumValue2) => doStuffForMyEnumValue2() //you will get warnings for non-exhaustive matches if you have more MyEnum subclasses than these case None => doStuffForNoEnum() }