CODEWITHSUNDEEP
scala
Kevin Meredith
Kevin Meredith

Reputation: 41939

Pattern Matching on Generic Trait's Parameterized Type

Given the following trait:

trait Foo[_ <: Product] {}

How can I pattern match on Foo's generic type?

In other words, is there a way to get at Foo's _ without using run-time reflection?

Upvotes: 1

Views: 213

Answers (2)

cmbaxter
cmbaxter

Reputation: 35463

This is possible, and I still think it's a duplicate as noted by my comment, but wanted to show how you can do it anyway. Credit to om-nom-nom for the original answer:

  trait Foo[_ <: Product]

  case class Bar(i:Int)
  case class Baz(s:String)  

  val fooBar = new Foo[Bar]{}
  val fooBaz = new Foo[Baz]{}

  checkType(fooBar)
  checkType(fooBaz)

  def checkType[T <: Product : TypeTag](foo:Foo[T]){
    foo match{
      case f if typeOf[T] <:< typeOf[Bar] => println("its a bar")
      case f if typeOf[T] <:< typeOf[Baz] => println("its a baz")
    }
  }

Upvotes: 1

Dima
Dima

Reputation: 40510

The whole point of _ as a type parameter is to specify that the type is unknown.

Upvotes: 1

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