How to pass Any to a generic method?

Question

I have a class that encloses and flatten a generic class (in order to contain a list of different generic typed instances):

trait XFun [P,V] {
  def apply(args: P): V
}

class XRoute (val handler: XFun[_,_])

class XRoutes (val routes: List[XRoute])

so that when I create XRoutes, it can contain a list of XFun with different generic types:

val routes = new XRoutes (List[XRoute](new XRoute(new XFun[Int,Int] {
  def apply[Int,Int](args: Int) = 0
}), new XRoute(new XFun[String, String] {
  def apply[String, String](args: String) = ""
}
))

However when I try to call it, it causes issue:

def parse(str: String) : Any = {/* impl */}

val inputObj = parse(inputString)
val outputObj = routes(1).handler.apply(inputObj)

This gives error on the apply line:

Type mismatch, expected: _$1, actual: Any

Currently my only solution is to create a reflected methods from MethodSymbol and call using reflectedMethod, but how do I achieve this without reflection?

Note that I do not want to change XFun to apply(Any):Any because I wanna type enforcement on the front end (e.g. when creating XRoute object, I want to do XFun[String,String] instead of having to do XFun[Any,Any]).

Answer 1

First of all I think your trait definition has too many types and should just be:

trait XFun [P,V] {
  def apply(args: P): V
}

And then you can just cast the object using asInstanceOf:

routes(1).handler.asInstanceOf[XFun[Any,Any]].apply(inputObj)

Note that this is not type safe and will fail at runtime if you pass the wrong type of argument to an XFun.