CODEWITHSUNDEEP
scala
Aashish Dattani
Aashish Dattani

Reputation: 131

Return Integer as AnyVal in Scala

I'm a newbie to Scala. I'm still trying to understand how method return types work in Scala. I have a base class as follows:

abstract class CustomNumber {
  def value: AnyVal
  override def toString = value.toString
}

And a subclass which looks like:

class CustomInteger(val input: Integer) extends CustomNumber {
  def value = input
}

But when I try to run this code, I get the error:

the result type of an implicit conversion must be more specific than AnyVal
  def value = input

type mismatch;
 found   : Integer
 required: AnyVal
  def value = input

Why would it be an error to return Integer as AnyVal if it is just a subclass?

Upvotes: 0

Views: 480

Answers (2)

Manoj Sehrawat
Manoj Sehrawat

Reputation: 1303

I think just change it to: 

class CustomInteger(val input: Int) extends CustomNumber {
  def value = input
}

Int is the scala type/class for integer. Have a look here for more details

Upvotes: 2

suish
suish

Reputation: 3343

AnyVal is the root class of all value types, which describe values not implemented as objects in the underlying host system. Value classes are specified in Scala Language Specification, section 12.2. https://www.scala-lang.org/api/current/scala/AnyVal.html

Just like it says, AnyVal is a root class of value types specified in Scala. And I assume you are using Java's Integer. Use Int instead fixes the issue.

PS It looks like you are trying to create a wrapper class of primitive types, That's where you should use value type using AnyVal.

Upvotes: 3

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