Scala type mismatch with generics ArraySeq[T] instead of Array[T]

Question

I have this method:

  private def doSomeStringProcessing[T](input: String, typeConverter: String => T): Array[T] = {
   cleanTheString(input)
            .split(",").map(typeConverter)
  }

which gives the error:

error: type mismatch;
[INFO]  found   : scala.collection.mutable.ArraySeq[T]
[INFO]  required: Array[T]

Per some googling, found posts saying to use the ClassManifest. Tried that and it was deprecated. So it pointed me to ClassTag. Googled that and found this resource which I'm trying to follow: https://docs.scala-lang.org/overviews/reflection/typetags-manifests.html#via-the-methods-typetag-classtag-or-weaktypetag

So I tried doing below:

  private def doSomeStringProcessing[T: TypeTag](input: String, typeConverter: String => T): Array[T] = {
   cleanTheString(input)
            .split(",").map(typeConverter)
  }

Which gives the exact same error. I want generics to make my code cleaner/easier to read, not convoluted, so I don't want to do any of the complicated solutions. What's the quickest way to fix this?

Adair · Accepted Answer · 2018-04-06 20:08:06Z

4

This does work with ClassTag (I got confused because IntelliJ imported and/or code-completed it wrong, so including the correct import below):

import scala.reflect.ClassTag

 private def doSomeStringProcessing[T: ClassTag](input: String, typeConverter: String => T): Array[T] = {
   cleanTheString(input)
            .split(",").map(typeConverter)
  }

answered Apr 6, 2018 at 20:08

Adair

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1 Comment

Max Wong Over a year ago

I had the same issue and your answer resolved my problem completely. Could you also please elaborate on the mechanism behind this? Thanks

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