What is the cleanest way to update (make a copy with a new value of) nested immutable data classes? ...

# getting-started

[Emil Aleborn]

What is the cleanest way to update (make a copy with a new value of) nested immutable data classes?
ArrowKt allows to simplify like this, but it does require kapt and annotations

val a = a.copy(
    b = a.b.copy(
      c = a.b.c.copy(
        d = a.b.c.d.copy(e = "Cumbersome update")
      )
    )
  )

// Using ArrowKt optics
val a = A.b.c.d.e.modify(a) { "Slick update" }

Are there any better alternatives?

[CLOVIS]

To my knowledge, there are no better ways currently. The value class KEEP contains a better way to do it, but it's still just a KEEP.

[knthmn]

There is this library that uses KSP instead of KAPT
https://kopyk.at/

[Emil Aleborn]

Thank you, I'll evaluate my options. 🙏

[MarinJuricev]

If it impacts your judgment on using Arrow and the @optics annotation is acceptable to you, Optics has an KSP plugin as well, you aren’t tied to just KAPT