Hello guys do you have any example of coroutine `SharedFlows

Question

Hello guys do you have any example of coroutine `SharedFlows` `shareIn` in github or gitlab I couldn t find good resources or articles with a sample What I am trying to achieve is combine flow1 flow2 with `shareIn` so I only need to `getfetch` once and share this to at least 3 fragments I really appreciate if someone could help Best Regards to all

Alexandre Brown · Answer

Hello < Johnjake Talledo> here is an example of `shareIn` or `stateIn` it s the same principle ```class MyClass override val coroutineContext CoroutineContext = Dispatchers Default CoroutineScope private val myPresentation SharedFlow lt Presentation gt = combine myRepository1 myStateFlow myRepository2 myStateFlow myRepository3 myStateFlow a b c gt myPresenter present a b c shareIn this SharingStarted Lazily fun getAbc = myPresentation ``` To get a StateFlow instead you would simply change the code to `myPresentation stateIn this SharingStarted Lazily presentDefaultValue ` Depending on what you want you might want to do `shareIn` only once in a property 1 instance or in the function call 1 instance per call In most cases having 1 instance is probably what you want but make sure it works with any 3rd party extension like `asLiveData` etc

ursus · Answer

watch out how you call getAbc you could get multiple instance and thuss no sharinv

Johnjake Talledo · Answer

< Alexandre Brown> Thanks a lot for this

Johnjake Talledo · Answer

< ursus> Can you please explain Thank you

ursus · Answer

in order to use shared flow you need to collect the same instance

ursus · Answer

otherwise there is no point in shareing

Johnjake Talledo · Answer

Yeah I haven t try it yet but my idea was collect the same instance in different fragment

Alexandre Brown · Answer

Hello < ursus> that s precisely what I discussed in the second part of the initial message It depends on what you want I would say make sure that using one instance works for your use case For example if using with the asLiveData

Alexandre Brown · Answer

In most cases one instance should be what you go for but make sure it works with any 3rd party implementation eg asLiveData and that you don t get collection exception To use 1 instance < Johnjake Talledo> simply add to `shareIn` at the end of the property and return that property in the function call see the updated code

Johnjake Talledo · Answer

Alexandre Thank you I will try it now and let you know once again thank you

Johnjake Talledo · Answer

< Alexandre Brown> What does the `myPresenter present a b c ` do Is this where you implement eg `asLiveData` in my case I use `MutableSharedFlow`

Johnjake Talledo · Answer

I am not sure if this correct

Alexandre Brown · Answer

< Johnjake Talledo> The `myPresenter present` is just hypothetical code that represents some transform Usually we use combine to listen to multiple flows and when we want to receive updates even if not all the flow changed Then inside the lambda of the combine we d use the various lambda parameters to perform some transformation eg Create a data class with some info from the various flows values If you don t want to merge multiple flows into 1 result and be notified of each updates in a single place then perhaps you don t need combine at all In your case it s much simpler You can simply do `private val deliveryUpdates SharedFlow = repository getDeliverable token id name count shareIn this SharingStarted Lazily ` Same principle for the `restaurentUpdates`

Johnjake Talledo · Answer

Thanks

Johnjake Talledo · Answer

< Alexandre Brown> I have question regarding `shareIn` or `Hot flows` when the app goes background does it still continue to emit if the end point has a new item or value

ursus · Answer

Flow knows nothing of androidl lifecycle

Alexandre Brown · Answer

Hello < Johnjake Talledo> as mentioned by < ursus> Flows are not lifecycle aware That being said when using Android databinding you can now it s very recent use StateFlow in your ViewModel and they will be lifecycle aware when used in data binding make sure to specify the lifecycle owner of the daya binding So Data binding currently supports StateFlow and LiveData You can learn more here

Johnjake Talledo · Answer

< Alexandre Brown> and < ursus> Thanks

Johnjake Talledo · Answer

< Alexandre Brown> unfortunately I do not use databinding only viewbinding ah I see so I just make flows lifecycle aware in my app actually its a complex network calls I had at least 5 network calls and then map this to data classes on one page that I want to optimized I just use the `getDeliverables` and `getRestuarant` as a test I was more familiar with `zip` in `rxJava` and `combine` is equivalent of `zip` and when I read about `ShareIn` this probably solve my problem what I wanted to achieve is to continue the `upstream` to fetch data from api then collect this in other fragment so I will not be calling the same expensive network calls because it takes sometimes 17 to 25 milliseconds before data on recycleview will show up