I have a network call that gets LiveData. The Live...

# android

[Ken Maffei]

I have a network call that gets LiveData. The LiveData is observed with my Fragment's lifecycle owner. Does the coroutine call I make also need to be scoped to the fragment's lifecycleowner? In other words should I use one of these, or does it not matter?

CoroutineScope(<http://Dispatchers.IO|Dispatchers.IO>).launch

or fragment.lifecycleScope.launch(context = Dispatchers.IO)

[Joost Klitsie]

How does this exactly look like? Are you combining coroutines with livedata?

[Joost Klitsie]

because I would do either the one or the other

[Joost Klitsie]

Also, it would make sense to not make network calls from your presenter but from a place that is separated from your UI, like a ViewModel

[Joost Klitsie]

In that case, the viewmodel can make the backend call, using viewModelScope and the fragment can observe that using livedata

[Joost Klitsie]

but if for some reason you want to launch it from the fragment, I'd use something like this pseudo code:

viewLifecycleOwner.lifecycleScope.launchWhenCreated {
    showLoading()
    val result = service.doBackendCall()
    showResult(result)
}

[Joost Klitsie]

What network library are you using?

[Joost Klitsie]

if you use Retrofit and you use the retrofit suspend functions, you don't have to use the Dispatchers.IO as Retrofit will take care of threading so you don't have to

[rkeazor]

No , you should however do liveData.post() rather than liveData.value

[rkeazor]

Also you can use the liveData builder that has it's own coroutinescope... val results = liveData { emit(apiFetch)}

[Joost Klitsie]

@rkeazor if you don't switch threads livedata.post is unnecessary

[Joost Klitsie]

But to answer the question properly we'd anyway need more info

[rkeazor]

@Joost Klitsie Hes making a network call, it shouldnt be on the main thread .. That's a given. He should be using Dispatchers.IO... so I'm not entirely sure what you mean🤷‍♂️

[Joost Klitsie]

@rkeazor Well as I said, if he uses retrofit with coroutines he doesn't need to use an io dispatcher as the retrofit library will take care of threading

[Joost Klitsie]

Also why use livedata if you can solve it with coroutines

[Joost Klitsie]

Also why use coroutines if he can solve it with livedata

[Joost Klitsie]

It depends a bit on his architecture and libraries

[rkeazor]

Livedata and coroutines are different .If hes using Livedata that means that he has active observers somewhere in his UI listening for the change (i.e: databinding, fragment , or activity) listening for the change... I think post is better for all none synchronous events. But your should use a liveDataBuilder instead

[Joost Klitsie]

well you are assuming he is doing it like that, but we don't know. Also post is for all non main thread -> main thread, so if you know you are on the main thread setValue is enough.

[Joost Klitsie]

But for this, it sounds like a livedata builder might do the trick

[Joost Klitsie]

but I don't know because there is not enough information

[rkeazor]

If your not observing a livedata. Why would you wrap data in it?