Is it possible (or are there plans) to have some sort of Swift-style

deinit

in Kotlin/Native?

Can you please elaborate your use-cases for this kind of feature?

Basically if you're writing a wrapper class for a C API, where you need to call one function to allocate a resource (image data or something) and another function to then deallocate it. Having these be coupled in a `init`/`deinit` setup tends to be cleaner than always having to remember to run

.destroy()

(or whatever) on the soon-to-be-deleted object. With Kotlin/Native being reference-counted similar to Swift (correct me if I'm wrong here), I figured it might be possible to do what Swift did with

deinit

.

You can pass a reference to

Arena

to the wrapper class that stores the allocated resource. Arena is designed to serve as a drop-in replacement for RAII pattern

in many cases, binding resource lifetime to object lifetime is not such a good idea, so we try to avoid finalizers/deinit as dangerous programming pattern

@olonho I would agree with you if we were talking about an environment with a "proper" garbage collector, but seeing as how reference counting is immediately and deterministically collected I feel like it would be a very natural relationship to couple the resource with its wrapper. Then again, I suppose Kotlin code should be somewhat compatible with all its environments.

Kotlin/Native is not a system with where objects are "immediately and deterministically collected", as we do employ cycle collector, whose behavior somewhat similar to typical GC (just on smaller graphs). So not sure if this argument is explicitly applicable. Also we may want to add additinal tracing collector in some future releases.

Oh, so

DeferScope

, which is implemented by

AutofreeScope

and

Arena

, does have the method

defer()

, which can be used similarily to Go's

defer

. Do I understand this correctly? Also, for my needs I added facilities similar to

java.io.Closeable

and

kotlin.io.use

. I would probably add extension method to register objects implementing this interface in

DeferScope

. Any chance something similar would be implemented in the stdlib?

@olonho Interesting. I didn't know about the cycle collector. That does complicate things.

@r4zzz4k

Oh, so

DeferScope

, which is implemented by

AutofreeScope

and

Arena

, does have the method

defer()

, which can be used similarily to Go’s

defer

. Do I understand this correctly?

Yes. It defers the lambda to be executed on arena disposal or

memScoped

end.

Also, for my needs I added facilities similar to

java.io.Closeable

and

kotlin.io.use

. I would probably add extension method to register objects implementing this interface in

DeferScope

. Any chance something similar would be implemented in the stdlib?

Resource management in Kotlin/Native is under a (long) discussion now, but we haven’t decided yet what exactly to be added to stdlib.

Got it, thanks!