Hi, I am evaluating the `Effects and contexts` par...

# arrow

[Tonis Ives]

Hi, I am evaluating the Effects and contexts part of the documentation. Docs seem to indicate that with function can be used by multiple arguments

suspend fun example() {
  db(connParams) { stdoutLogger {
    with(object : Database by this@db, Logger as this@stdoutLogger) {
      saveUserInDb(User("Alex"))
    }
  } }
}

However, the Kotlin std defines with with single argument

public inline fun <T, R> with(receiver: T, block: T.() -> R): R {

Which with function should I use?

[simon.vergauwen]

That uses the with with a single argument, but uses a special technique that allows for creating an anonymous object that implements multiple interfaces.

It used to work at the time, not sure which Kotlin version. Is that not working anymore? It was discovered by @Alejandro Serrano Mena

[Tonis Ives]

Do you have sample code for that part? I can share my gist, but yeah it’s not compiling. It might be because not all functions are available in the sample and I tried to implement them myself.

[Kristian Frøhlich]

Still working. You can do something like this:

@Suppress("SUBTYPING_BETWEEN_CONTEXT_RECEIVERS")
inline fun <reified R, reified T1, reified T2, reified T3> with(
    t1: T1,
    t2: T2,
    t3: T3,
    block: context(T1, T2, T3) (TypeWrapper<T3>) -> R
): R {
    return block(t1, t2, t3, TypeWrapper.IMPL)
}

sealed interface TypeWrapper<out T> {
    object IMPL : TypeWrapper<Nothing>
}

[simon.vergauwen]

Yes, that works but it's not what is happening here @Kristian Frøhlich. That examples predates context receivers

[simon.vergauwen]

@Tonis Ives I don't have the full example on hand, I can try reproducing it later to see if it still works

[Kristian Frøhlich]

Ah 👍

[Tonis Ives]

I’m sorry, I forgot to include my gist. There are more errors after the f error

[Alejandro Serrano.Mena]

I think this worked at some point, but as of now you either define a new version like @Kristian Frøhlich did, or you nest several with

[Alejandro Serrano.Mena]

we should definitely check the documentation, though