Sealerate is a small (3rd-party-dependency-free) library that provides convenience functions values[T] and collect[T] that dynamically create a set of all instances of a sealed class.

Sealerate is available for Scala 2.10, 2.11, 2.12, and 2.13. If you are using sbt, add the following to your build.sbt:

libraryDependencies += "ca.mrvisser" %% "sealerate" % "0.0.6"

package example

import ca.mrvisser.sealerate

sealed trait Switch
object Switch {
    case object On extends Switch
    case object Off extends Switch

    /**
     * Enumerate all instances of of the [[Switch]] trait
     */
    def values: Set[Switch] = sealerate.values[Switch]
}

Now Switch.values will provide Set(On, Off), and will update automatically when new objects are added.

Note that a compilation error is thrown if the following conditions aren't met:

• The given type T is not a sealed trait, sealed abstract class or sealed class
• The case instances of type T are not all case objects. (As an alternative the collect[T] function will simply filter out case classs instead of throw an error)

• Branden Visser (core maintainer)
• jibbers42 (Scala 2.12 support)
• Philippus Baalman (Scala 2.12 & 2.13 support)
• Travis Brown (library based on his StackOverflow post)