Scala case class method: `public scala.collection.Iterator productElementNames()`

Question

if we have a look into the bytecode produced by this case class compilation


case class Person(name: String, age: Int)

we get besides others this method:


public scala.collection.Iterator<java.lang.String> productElementNames();

So, the question is, where it comes from and why it can not be called on a Person's instance like, for instance the other one from the same compiled class

public scala.collection.Iterator<java.lang.Object> productIterator();

I use this versions:


$ scala -version                                                                                                                                                                                              
Scala code runner version 2.13.8 -- Copyright 2002-2021, LAMP/EPFL and Lightbend, Inc.

$ scalac -version                                                                                                                                                                                             
Scala compiler version 2.13.8 -- Copyright 2002-2021, LAMP/EPFL and Lightbend, Inc.

idea screenshot

https://github.com/scala/scala/blob/2.13.x/src/library/scala/Product.scala — Dmytro Mitin, Oct 21 '22 at 12:08
*"why it can not be called on a Person's instance like..."* Why did you decide that it can't be called? — Dmytro Mitin, Oct 21 '22 at 12:09
https://stackoverflow.com/questions/60999247/how-can-i-view-the-code-that-scala-uses-to-automatically-generate-the-apply-func/ — Dmytro Mitin, Oct 21 '22 at 12:21
https://scastie.scala-lang.org/DmytroMitin/GcOc9Oz2SlmN2SoGUIApig/1 — Dmytro Mitin, Oct 21 '22 at 12:23
it definitely can be called, what makes you think it cannot? — ElectronWill, Oct 21 '22 at 12:30

apnmrv · Answer 1 · 2022-10-22T15:17:16.013

1

Solved

thanks to @DmytroMitin and @ElectronWill

Yes, productElementNames() is a method inherited from the Product.

It is definitely callable in Scala 2.13.8, with which the sample is compiled.

The problem was, that the IDE thought it was Scala 2.12.4, where the Product did not yet contain that method.

edited Oct 22 '22 at 15:17

answered Oct 22 '22 at 13:56

apnmrv

21
3

You can always check whether your code compiles with `sbt clean compile`. Don't rely completely on what your IDE says. – Dmytro Mitin Oct 22 '22 at 14:56

Scala case class method: `public scala.collection.Iterator productElementNames()`

1 Answers1