Question

I have two functions with different type signatures, and I want to store them both in a Map:

val add = ((a: Int, b: Int) => a + b)
val odd = ((a: Int) => a % 2 == 0)

var funcs = Map[String, Any]("add" -> add, "odd" -> odd)

Then I want to access these functions at a later date, without having to know about their types. How would I do this? I can write:

funcs("add").asInstanceOf[(Int, Int) => Int](1, 2)

But that requires me to either

1. know ahead of time what the type of the function is
2. do some sort of pattern match that accounts for every possible type.

Is there some way I can find out the type of the object stored as Any and convert it to that type?

Answer 1

Although this certainly is not a good idea, if you really have to do it, you can do it using reflection.

Using PaulP’s Invocation utility:

scala> val add: (Int, Int) => Int = _ + _
add: (Int, Int) => Int = <function2>

scala> val isOdd: Int => Boolean = _ % 2 != 0
isOdd: Int => Boolean = <function1>

scala> import Invocation._
import Invocation._

scala> val funcs = Map("add" -> add, "isOdd" -> isOdd)
funcs: scala.collection.immutable.Map[java.lang.String,ScalaObject] = Map(add -> <function2>, isOdd -> <function1>)

scala> funcs("add") o 'apply(3, 4)
res18: Any = 7

scala> funcs("isOdd") o 'apply(11)
res19: Any = true