Hello Can somebody tell the difference between Async Await i

Question

Hello Can somebody tell the difference between Async Await in C JS and Async coroutines in Kotlin I read the docs of both Async await in c amp Async in Kotlin Both lets you do the asynchronous programming without blocking the thread So except the syntax Is there any difference Is there any upper hand of Async coroutine in Kotlin

serebit · Answer

``` async suspendingFunction await ```

serebit · Answer

Coroutines in Kotlin have a lot more flexibility and a larger feature set than basic async await in JS

gildor · Answer

Probably not the best example of async await usage

gildor · Answer

Rohan introduction to coroutines talk covers this topic <https www youtube com watch v= hfBv0a09Jc>

kenkyee · Answer

They conceptually all do the same thing make more efficient use of a single thread or threads than regular threading by suspending code that has to wait on that thread

gildor · Answer

But recommended way to use coroutines in Kotlin is different there is a concept of suspend function and async await used only for explicitly asynchronous code This difference covered in this talk and official guide

Rohan Maity · Answer

Thank you I watched the intro video to coroutines What I Inferred from video is Async await in c are keywords where async await are library functions Now 1 how do this thing give more flexibility 2 is just about the flexibility if only comparing async await in c with async in Kotlin or is there any other upper hand Also one thing I can think of is async starts coroutines And Coroutines are lighter than Threads So does this thing make async better than async await in C Correct me if I am wrong please

gildor · Answer

Kotlin coroutines is not only async await and it s main point of Kotlin implementation because language has only support of `suspend` functions and very basic builders no async awiat in the language Even now in Kotlin on base of this implemented not only async await but also generators Go style channels which also based on coroutines but part of the language actors and so on So this is definitely more flexible So async await implementation in Kotlin and C is not so different in terms of use cases but it s just a small part of kotlinx coroutines and actually not even part of language or stdlib Also default style recommended for kotlin is not async await but usage of sequential suspend functions

gildor · Answer

One more difference about async await that in Kotlin all coroutines builders use structured concurrency pattern so always have parent that control their lifecycle and prevent async tasks leaking

gildor · Answer

gt async starts coroutines And Coroutines are lighter than Threads So does this thing make async better than async await in C I didn t get your question

Rohan Maity · Answer

< gildor> thanks for such good answer I got it Suspending functions are flexible And async is also built on the top of suspending function Coroutines are great I also tried async await in c To check out the difference For use case and in working they do not seem different Only difference I found out was that of one in c are keywords and one in Kotlin are functions on the top of suspending But in the talk It is said Kotlin async only async not Coroutines as whole provides better flexibility than async await in other languages as in Kotlin async are functions whereas in other languages these are keywords If you don t mind can you give a simple example where async only async not Coroutines as whole being flexible than async await

gildor · Answer

gt If you don t mind can you give a simple example where async only async not Coroutines as whole being flexible than async await edited For example recently async and other coroutine builders launch actor etc reimplemented on top of StructuredConcurrency new approach where you always has parent of any async operations and cannot just run standalone coroutine with no lifecycle handling you can but you should do this explicitly in GlobalScope More info <https medium com elizarov structured concurrency 722d765aa952> If async await would be just keywords it wouldn t be possible to change but because async is just a library function same as Job Dispatchers etc you can change implementation Also async await in C always works with Task which is promise like abstraction of C but in Kotlin Coroutines you can write await implementation for any promise like abstraction and just call it `myCustomFuture await ` which is also very powerful and flexible way which would be possible with keyword or must provide some built in API for integration which can have some limitations

gildor · Answer

One more difference in C you mark your function with `async` but in Kotlin it s not recommended you rather wrap to `async` builder on call site to be explicit about concurrency and in Kotlin instead of use async on function declaration and return Deferred lt T gt you will just return T and mark function as suspend

Rohan Maity · Answer

< gildor> I read the article Since async are functions so they can be supplied with scope If scope runs out coutines will stop But this is not possible with async await keywords method lifecycle handling is not possible Is that so Also very much thanks to point out that we can change implementation of await This was I was looking for To change the implementation I have to supply my version in onAwait

gildor · Answer

gt But this is not possible with async await keywords method lifecycle handling is not possible You of course can include this to language if you want but usually it s much harder and you cannot break backward compatibility which actually happen And StructuredConcurreny not a part of C or Go but was originally proposed for Go and now to add it it requires significant language changes which not a problem in case of Kotlin

gildor · Answer

gt To change the implementation I have to supply my version in onAwait edited What do you mean `async `is just a coroutine builders that provide own promise like abstraction If you already have some you can implement `await ` function for it you don t need `async` or `Deferred`

Rohan Maity · Answer

Ok So If want the await implementation different I have to implement my own CoroutineBuilder

gildor · Answer

no you don t need coroutine builder for existing promise future abstraction

gildor · Answer

See for example integration with Guava LisenableFuture <https github com Kotlin kotlinx coroutines tree master integration kotlinx coroutines guava> or with Java 8 CompletableFuture

gildor · Answer

But you can have coroutine builder that actually creates coroutine that converted to some other Promise it can be useful as adapter for Java code which cannot use suspend functions directly easily see CompletableFuture builder <https github com Kotlin kotlinx coroutines tree master integration kotlinx coroutines jdk8>

Rohan Maity · Answer

Thanks < gildor> not only I cleared my doubt I also got to know some more things