标量反射：将符号与给定值匹配

Question

I'm trying to match a class constructor (from the set of alternatives) against a list of values that are retrieved from parsing some DSL. As these values are heterogeneous, I store them in an Array[Any] .

I'm using the following piece of code to do so:

val myClassSymbol: ru.ClassSymbol = mirror.classSymbol(Class.forName(myClassName))
    val cm: ru.ClassMirror = mirror.reflectClass(myClassSymbol)
    val ctor = myClassSymbol.primaryConstructor.alternatives find { c =>
      val signature: ru.Type = c.typeSignature
      val constructorParams = signature.paramLists.flatten
      val constructorParamValues: Seq[Any] = resultOfMyParsing
      (constructorParamValues.size == constructorParams.size) && ((constructorParams zip constructorParamValues) forall ((pair: (ru.Symbol, Any)) => {
        val sym = pair._1
        var param = pair._2
        ??? // something to match the symbol with the value
      }))
    }
 ctor map {c =>
      val ctorm = cm.reflectConstructor(ctor.get.asMethod)
      ctorm(resultOfMyParsing: _*)
    } getOrElse {
      throw new IllegalStateException(s"cannot find ctor for $constructorParamValues") // might be relace with some clever logic as a fallback
    }

Has anyone an idea what to replace the ??? with? (or come up with a better/simpler solution altogether)

Many thanks in advance!

Answer 1

I think that the best you can do in general is to compare classes (due to type erasure):

val clazz = mirror.runtimeClass(sym.asTerm.typeSignature)
clazz.isInstance(param)

This will need to be modified a bit if you want to handle by-name constructor parameters.