Is there any way to write this using a function reference (e.g. `::emit`)? ```suspend fun FlowCollec...

# getting-started

[Mark]

Is there any way to write this using a function reference (e.g. ::emit)?

suspend fun FlowCollector<Something>.emitNotNull(something: Something?) {
    something?.let { emit(it) }
}

[spand]

Cant you ask intellij to convert it ?

[Mark]

It doesn’t come up with any such recommendation. So perhaps not possible

[nanodeath]

does ?.let(FlowCollector::emit) not work?

[spand]

Ah, I think there are limits to method references and suspend functions

[Mark]

I suppose anyway should be using also but then get similar:

Type mismatch.
Required:
(TypeVariable(T)) → Unit
Found:
KSuspendFunction1<Something, Unit>

[Mark]

This works:

suspend fun FlowCollector<Something>.emitNotNull(something: Something?) {
    something?.suspendingAlso(::emit)
}

suspend inline fun <T> T.suspendingAlso(block: suspend (T) -> Unit): T {
    block(this)
    return this
}

[spand]

Your ::emit is this::emit . I am not sure this is what you want? ie. creating a bound reference on every call. In any case I think this is much more readable (but maybe your example is contrived):

suspend fun FlowCollector<String>.emitNotNull(something: String?) {
        if (something != null) emit(something)
    }

[Mark]

Yes, I agree that’s much better. Just figuring out why some things don’t work :)

[spand]

I think what threw me off at first was that FlowCollector::emit is actually a two parameter function. One for the receiver and one for the value to emit. This doesnt work nicely with let and method reference. The reason it works as a lambda is that receiver is passed implicitly.

[Mark]

I don’t think that’s the issue. ::emit would work if emit was not suspending?

fun FlowCollector<Something>.notSuspending(something: Something?) {
    
}

suspend fun FlowCollector<Something>.emitNotNull(something: Something?) {
    something?.also(::emit) // does not compile
    something?.also(::notSuspending) // does compile
}

[spand]

Right. There is the suspending part also. Mostly I am just talking about this because I see this::emit as a work-around to my issue (and not generally desirable).

[Mark]

Isn’t this::emit synonymous with ::emit ?

[spand]

Yes. I meant vs FlowCollector::emit

[spand]

Lets just stop here. Its just turning into me rambling