Hi I want to use the `select` clause to select between two u

Question

Hi I want to use the `select` clause to select between two user inputs two button clicks Should I implement the select clause myself in an extension function or should I transform the button clicks to a channel and then use the already existing select clause implementations

gildor · Answer

Channel implementation would be probably more heavyweight than just 2 callbacks but at least it already works

groostav · Answer

< gildor> heavyweight handling button clicks how many million clicks per second do you need

Dominaezzz · Answer

I d say use an extension function Channel would be be overkill

louiscad · Answer

Is anyone aware of a digest example on how to make a select clause implementation The Channel implementation is a lot of code for me to see clearly how I should do it

gildor · Answer

Each channel creates more objects and each callback handling involves allocations and atomic usages because channel is multi thread abstraction Of course on practice you will not see difference my point that just for 2 callbacks you can provide more efficient and simple implementation

louiscad · Answer

BTW performance doesn t need to be optimal in my case it s an internal TornadoFx app that needs to register some devices

gildor · Answer

< louiscad> Depends on API which you want to get I don t see why you need coroutines in this case

gildor · Answer

in general just subscribe on both callbacks and call another callback nothing trickt

louiscad · Answer

It s not that I need coroutines but I want to make the whole code sequential I have a `UserAction` sealed class hierarchy that I want to return from a suspend function implemented in the UI code

gildor · Answer

``` fun onClick v1 View v2 View onClick View gt Unit v1 setOnClickListener onClick it v2 setOnClickListener onClick it ```

gildor · Answer

If you want to use coroutines use `suspendCoroutine` instead of onClick lambda

louiscad · Answer

You re right `suspendCoroutine` may be enough for my use case I was over complicating things Thanks for your insight

Dominaezzz · Answer

Instead of a channel why not use a Deferred

gildor · Answer

Something like this ```suspend fun awaitClick v1 View v2 View View return suspendCancellableCoroutine cont gt val onClick View gt Unit = cont resume it Not sure about this part but probably make sense cont invokeOnCancellation v1 setOnClickListener null v2 setOnClickListener null v1 setOnClickListener onClick v2 setOnClickListener onClick ```

gildor · Answer

Or even ``` suspend fun List lt View gt awaitClick View return suspendCancellableCoroutine cont gt val onClick View gt Unit = cont resume it Not sure about this part but probably make sense cont invokeOnCancellation forEach view gt view setOnClickListener null forEach view gt view setOnClickListener onClick ```

louiscad · Answer

It s a bit more complex still as I want to disabled the buttons as soon as one is clicked plus the user may abandon something that happens next where I d need to enable back both buttons and wait for click on one again but I think I ll figure it out

gildor · Answer

Still can be handled using the same approach

louiscad · Answer

Yes that s why I put a thumbs up on your snippet

gildor · Answer

sorry fixed example with `List lt View gt `

louiscad · Answer

I saw the mistake for this one haha wink

Zach Klippenstein (he/him) [MOD] · Answer

< louiscad> if you re still looking for a simpler select clause implementation I wrote a gist a while back

louiscad · Answer

Thank you < Zach Klippenstein he him MOD > while I could do without select clause thanks to Andrey s help it s still interesting and it may help for future use cases +1