Im sure everyone else knows this, but i havent bee...

# getting-started

[Ben Butterworth]

Im sure everyone else knows this, but i havent been able to google/ stackoverflow this: in scope.launch{} , what do you call those curly braces? I know the last parameter type seems to have to be a lambda, often called block

[Ben Butterworth]

Is launch a scope function? Im not able to confirm

[Ben Butterworth]

I mean it literally is a function of the variable scope in my case 😂, but i meant Kotlin “scope functions”

[nanodeath]

I think it's a lambda? if it's not inline, syntactic sugar for an anonymous inner class

[nanodeath]

I can't exactly tell from here, but it looks like the signature would be fun launch(callback: () -> Unit), aka fun launch(callback: Function1<Unit, Unit>)...I think.

[nanodeath]

I know the last parameter type seems to have to be a lambda, often called block

I mean, this seems accurate

[nanodeath]

https://kotlin.github.io/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines/launch.html this is the actual doc

[Ben Butterworth]

Yes, but i dont know what the curly braces mean. What can i call it? Its not a lambda, because it doesnt have ->

[Ben Butterworth]

Also, if it were a lambda, the implicit keyword would be it, but its actually this

[Ben Butterworth]

this is the receiver argument, and it is the first argument of the lambda. https://stackoverflow.com/questions/60485368/kotlin-difference-between-it-and-this-keyword

[nanodeath]

it's still a lambda, just without an argument and with a different receiver

[nanodeath]

CoroutineScope.() -> Unit is as much a lambda as (Int) -> Double is

[Ben Butterworth]

just to be clear, those are not lambdas, but lambda types? 😂 i think i understand

[nanodeath]

yeah. I'm not 100% on the terminology but it's at least close. maybe someone else can chime in.

[Ben Butterworth]

i cant believe theres only 3 upvotes on that stackoverflow question

[Ben Butterworth]

Thanks for pointing me in the right direction

[nanodeath]

it's a little weird that the top answer is talking about scope functions -- as far as I can tell, that's exclusively referring to let/also/apply/run/with. but any method can accept a lambda type that has a custom receiver

[nanodeath]

words are hard

[Ben Butterworth]

i think that answer is kinda wrong, because as you say, this is applicable to all functions that take a lambda with receiver, not just scope functions

Scope functions: There are five such functions included in the Kotlin standard library: apply, run, with, let, and also.

https://kotlinlang.org/docs/reference/scope-functions.html
Edit: Edited with official link

[brandonmcansh]

CoroutineScope.() -> Unit is an example of the use of the optional receiver type (CoroutineScope in this example) with the block/function being called on the receiver as opposed to (CoroutineScope) -> Unit

[Dennis]

trailing lambdas?

[Ben Butterworth]

great confusing combo, trailing lambda with receiver. but it was basically the trailing lambda syntax that was confusing me

[caelum19]

Pro tip, highly recommend having this handy https://kotlinlang.org/docs/kotlin-docs.pdf. You can skim the table of contents for something that sounds like what you're looking for, and discover things that you wouldn't otherwise 🙂

[Ben Butterworth]

thanks @caelum19, i just read this 2 months later xD, skimming now