获取Scala中的所有枚举案例对象值

Question

In Scala, enums are a disputed area and many people (including myself) rather use case object s than any library-based enumeration. This is great, except for that one doesn't get a list of all possible values, which sometimes is needed. I've maintained such lists ( allKeys ) manually, but that is tedious and error-prone.

The question is: how can Scala 2.11 TypeTags or reflection be used, to create such a list?

One of two ways would work:

• getting all derived instances of a sealed class
• getting all case object s declared within a particular object

Note: There are samples that seem to promise what I'm looking for. But that's overkill - there must be an almost one-liner to get the same?

Below is a test for this. How could I implement the allOf function?

class ManifestToolsTest extends UnitTest {

  behavior of "ManifestTools" {

    sealed class MyEnum

    object MyEnum {
      case object A extends MyEnum
      case object B extends MyEnum
      case object C extends MyEnum

      val x= 10           // should not be listed
      def f(x: Int) = x   // should not be listed
    }

    def allOf[T]: Seq[T] = {
      ...  
    }

    it should "be able to list the 'case object' members of an object" in {

      val tmp: Seq[MyEnum] = allOf[MyEnum]
      tmp should contain theSameElementsAs( List(MyEnum.A, MyEnum.B, MyEnum.C) )
    }
  }
}

I've tried to get this info from the Scala documentation, but when it comes to reflection, things are really abstract. I believe the above need is (should be) covered by Scala 2.11.

References:

• Case objects vs Enumerations in Scala

Answer 1

我找到了治疗方法 ，名为Enumeratum，但我认为无论如何我都会发布这个问题，以便人们更容易找到这件新的宏观珠宝。