Does anybody know a solution for this problem? <https://stackoverflow.com/questions/54327143/how-to-...

# multiplatform

[addamsson]

Does anybody know a solution for this problem? https://stackoverflow.com/questions/54327143/how-to-create-a-dynamic-proxy-in-kotlin-common-code

[gildor]

You cannot. This is jvm only feature

[gildor]

But you can use expect/actual declaration and extract this code to jvm and implement in some different way in other platforms

[addamsson]

do you know about a library which does this?

[addamsson]

Seems like that there is a proxy object in javascript as well

[addamsson]

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Proxy

[Ema]

@gildor do you know if kapt based approaches are even possible? Generating instead of reflecting code?

[Dico]

You can generate code with kotlin dynamically on the jvm, so yes. It's a very powerful feature.

[Ema]

how about, generate code on KN?

[gildor]

do you know about a library which does this?

Does what? proxy?
It’s platform specific API so should be done on platfrom specific code.

[gildor]

@Ema Kapt based on Java APT, so it’s JVM only API
But you can use it to generate some Kotlin code that can be used on any platform. It will be additional build step, where you generate some common code, than build it using MPP

[addamsson]

I think I'll try to reconcile javascript's proxy with java's proxy instead

[addamsson]

and provide a common api for it

[addamsson]

i don't really want to generate code

[addamsson]

or have my users bother with it

[addamsson]

thx for the ideas 👍

[Davide Giuseppe Farella]

@addamsson I’m in the same limbo here 😄 Actually I’m using Proxy on Jvm and TODO() on KN & JS, since they aren’t my priority actually and hoping in a better solution than code-gen, please keep in touch here on StackOF, I’ve starred your post, just in case

[addamsson]

TODO()

this literally made me laugh out loud 😄

[addamsson]

👍

[Davide Giuseppe Farella]

TODO() is the developers’s 42 😄

[gildor]

just curious what is your use case for Proxy

[Davide Giuseppe Farella]

That's mine https://github.com/4face-studi0/Ermes
Tbh I'm also curious about Adam

[gildor]

So Retrofit like use case. Yeah, I see

[gildor]

I don’t think that it will be possible to implement something like this for MPP before Compiler Plugins API will be available

[gildor]

or some another approach, like function delegation, but it also requires language support

[gildor]

For now I just use ktor-http-client for this (but also use interface to abstract it)

[Davide Giuseppe Farella]

For now I'm just exploring kotlin multiplatform and I'm very happy to see at least the jvm part is working. Then, with time, I'll see if "something new" will come to kotlin-mp to help me on that, or maybe choose a complete different approach.

[addamsson]

@Davide Giuseppe Farella I did some research

[addamsson]

I tried using javascript's Proxy as an external class

[addamsson]

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Proxy

[addamsson]

but it quickly turned out that javascript's proxy is not a real proxy

[addamsson]

when you careate a proxy for a Foo interface you get back a Proxy and not an object which implements Foo

[addamsson]

so I'm kinda stuck with this idea

[addamsson]

while Java's proxy works as it is supposed to work javascript's proxy does not adhere to the proxy pattern

[Davide Giuseppe Farella]

So basically

interface Foo {
    fun bar(): Int
}

become

class Proxy {
    fun bar() = 4 // for instance
}

?

[addamsson]

no, the whole point would have been to supply an interface

[addamsson]

and get a proxy instance back like

[addamsson]

val foo: Foo = createProxyFrom(Foo::class)

[addamsson]

this is the proxy pattern

[addamsson]

but javascript doesn't support it

[Davide Giuseppe Farella]

Yes, I just didn’t understand what that Js lib does instead of that

[Davide Giuseppe Farella]

I mean, at runtime, my Foo interface implementation become ( basically )

class FooImpl: Foo {
    override fun bar() = 4
}

[Davide Giuseppe Farella]

What about that Proxy lib?

[addamsson]

this is not a lib but a built-in class in javascript

[addamsson]

what it does is that you give it an object

[addamsson]

it wraps the object

[addamsson]

and you use the proxy from that point like it was that object

[addamsson]

given javascript's dynamic nature it is not a problem that you get back a Proxy instead of a Foo

[addamsson]

but this is a problem in Kotlin since you can't cast a Proxy to a Foo

[addamsson]

I pasted a link to the docs above ☝️

[Davide Giuseppe Farella]

Ok, so I get it right, basically I’ll have
class FooImpl : Foo

[Davide Giuseppe Farella]

I’m taking a quick look at that

[Davide Giuseppe Farella]

Anyway maybe that could fit my usecase, I’ll need more valutations. Thanks for now

[addamsson]

👍