working with class as function parameter in Scala-CodePudding

Let's say I have the following function:

def sampleFunc (c : Class[]) : Boolean

It takes a class as parameter. It then checks if a certain element el is of type Class[]. I tried accomplishing that by doing

el.isInstanceOf[Class[]]

But that doesn't work, it always returns false. Does someone see what I'm doing wrong here?

CodePudding user response：

c.isInstance(el)

is the dynamic equivalent of the instanceof operator in Java (i.e. the isInstanceOf method in Scala).

CodePudding user response：

You need to use a type class scala.reflect.ClassTag[T]

import scala.reflect.ClassTag
import scala.reflect.classTag

def sampleFunc[T: ClassTag](el: Any): Boolean = {
  classTag[T].runtimeClass.isInstance(el)
}

or via pattern matching

def sampleFunc[T: ClassTag](el: Any): Boolean = {
  el match {
    case _: T => true
    case _    => false
  }
}

However, el.isInstance[T] is still not supported because of type erasure in java.

Now

println(sampleFunc[String](""))
println(sampleFunc[String](1))

will print true and false respectively.