how can I use kotlin-reflect to get all subclasses of an abstract base class? the base class is NOT ...

# announcements

[Peter Ertl]

how can I use kotlin-reflect to get all subclasses of an abstract base class? the base class is NOT sealed

[Marc Knaup]

Using solely kotlin-reflect? There is none.
On JVM you’d have to use Java API to scan all classes in all packages in all classpaths and then check if they’re a subclass. Neither performant nor too reliable.

[Peter Ertl]

Ok well too bad - thanks @Marc Knaup

[thanksforallthefish]

that, I think, is exactly the point of sealed classes and why the compiler can check exhaustive `when`s for instance. if it was easy to do without too much overhead there would not be a need for sealed 😄

[Peter Ertl]

i love sealed classes … only issue is the files tend to get really large

[Peter Ertl]

even when stripping off as much as you can from the sealed classes and relocating logic elsewhere

[Marc Knaup]

@Peter Ertl for Kotlin 1.5. they’re working on allowing you to have subclasses of sealed classes in different files of the same project & package.

[Peter Ertl]

that will be the nirvana of coding 🙂

[Peter Ertl]

jetbrains +1

[Peter Ertl]

can’t wait for it 🙂

[Marc Knaup]

We also get sealed interface :)

[Peter Ertl]

yeah, even more goodness

[Peter Ertl]

they are so kind to release us from the burden of java code which feels so 1990

[Marc Knaup]

Exactly. Just the interoperability with Java prevents some features from reaching their maximum potential.

[Peter Ertl]

I am really amazed on how close to “real” pattern matching (like in haskell, scala, etc.) you can come with sealed classes.

[Peter Ertl]

kotlin is just so “wow”

[Peter Ertl]

I converted a current project in a company I am freelancing for from java to kotlin

[Peter Ertl]

it’s just a 180 degree turn from boredom to fun

[Peter Ertl]

I always hoped that scala will make it somehow but they always denied java so interop is a PITA and scala 3 comes too late with too little… so kotlin made life meaningful again (and I can do functional stuff easier without looking for a haskell project) … thanks to all you guys (I assume you are part of the jetbrains team)

[Marc Knaup]

I am not. Just using Kotlin way too much.

[Marc Knaup]

And building way too many libraries along the way 😄

[Peter Ertl]

ok … anyway … you can’t use too much of kotlin imho

[thanksforallthefish]

to be fair java is aware and trying to overcome some limitation. I am not much interested in going deeper, but project amber is introducing sealed classes, records (akin to data classes) and pattern matching (more powerful than what you can currently do in kotlin)

[thanksforallthefish]

https://openjdk.java.net/projects/amber/

[thanksforallthefish]

I guess they got scared of the traction kotlin got

[Peter Ertl]

true, but they will always suffer from their legacy and it’s getting harder and harder to implement cool stuff without dropping some cruft

[Peter Ertl]

I guess kotlin scares the hell of of them

[thanksforallthefish]

problem is, for java, this feature will be available on Android in ~100 years

[Marc Knaup]

I hope Amber moves faster than Project Valhalla which started 6 years ago and still isn’t done 😅

[Peter Ertl]

kotlin could always decide to drop jvm support and compile to native or their own jvm implementation (though I don’t expect them to)

[Peter Ertl]

they always have an option but oracle does not

[Marc Knaup]

They already have their own VM for Native - more or less. Over time JVM could easily become obsolete for Kotlin.

[Peter Ertl]

full ack

[thanksforallthefish]

records are definitely available already, so I guess everything delivered is usable, provided a recent enough jvm. the delivery every 6 months rather than by feature makes things so much faster

[thanksforallthefish]

as an impression. the idea of agile