Declaring ``` class MyClass { fun CoroutineSco...

# announcements

[Davide Giuseppe Farella]

Declaring

class MyClass {
    fun CoroutineScope.run() 
}

MyClass become the context of run(), while CoroutineScope become the "owner".
That makes sense... But what I want the opposite effect?

Sometimes I use this pattern

class Mapper<E, P> {
    fun <T> invoke( block: Mapper.() -> T ): T
    fun E.toPojo(): P
    fun P.toEntity(): E
}

And makes sense that Mapper is the context for call mapper { entity.toPojo() }

But back to the first example, doesn't make sense to call

launch {
    with( myObj ) { run() } 
}

I would simply call

launch {
    myObj.run()
}

Is that possibile?

[ghedeon]

This question just keeps giving simple smile . It's being asked at least once a day: https://kotlinlang.slack.com/archives/C4GKV43N2/p1547761639036700
https://kotlinlang.slack.com/archives/C1CFAFJSK/p1548745279640400
https://kotlinlang.slack.com/archives/C1CFAFJSK/p1548746361645400
https://kotlinlang.slack.com/archives/C0B8M7BUY/p1548789314601600

[ghedeon]

Basically yes, you either do with( myObj ) { run() }, or you pass the scope as a parametr and do myObj.run(scope).

[ghedeon]

@Allan Wang mentioned some alternatives, tho. With cancellableCoroutine or yeld. I'm curious to see some examples.

[Davide Giuseppe Farella]

Ops 😅 I hoped in a fancier way to do that 😁

[ghedeon]

aren't we all? 🧌

[ghedeon]

it's all shine and roses when the caller is close to the fun definition. But if you start thinking of deeper callstack, through your domain, data layer... ugh. Let say you put CoroutineScope in all your public methods, later you refactor and realize that for a particular case suspend is enough and scope param is redundant? How many places do you need to change now? 🤔 What if you change your mind the next day?

[Davide Giuseppe Farella]

Usually I use suspend everywhere, but in this case I don't care about the "lifecycle" of this function, I just care about results returned by `Channel`s

[Davide Giuseppe Farella]

https://github.com/4face-studi0/FreshTv-android/blob/master/playlistsource/src/main/java/studio/forface/freshtv/playlistsource/parser/PlaylistParser.kt

[Davide Giuseppe Farella]

That's my use case

[Davide Giuseppe Farella]

The best solution I found as now

suspend operator fun <T> MyClass.invoke( block: suspend MyClass.() -> T ) = block()

launch { myObj { doSmtng() } }

[Davide Giuseppe Farella]

Basically the same pattern described for Mapper above 😔