I use Channels to send one-off events from my View...

# coroutines

[Florian]

I use Channels to send one-off events from my ViewModel to my fragment. What should I use for events that should only be received once at most? ConflatedChannel for some reason still allows multiple events to be sent.
Right now I have this:
(receive suspends till an event is sent over the channel, but the return type is Unit so I ignore the return value)

[gildor]

Why "for some reason"? Conflated channel is essentially observable state, which doesn't complete (until it closed)
Instead of channel I would use suspend function, which under the hood could use CompletableDeffered, it's the easiest way to have a single value which is suspended until deferred is completed

[Florian]

is this suited to communicate from the ViewModel to the Fragment?

[Florian]

right now I use normal Channel + receiveAsFlow and then for events that are only supposed to happen once I use take(1) (just to make sure). What do you think about that?

[gildor]

Yes, nothing special in communication between view model and a fragment

[Florian]

Well, the special part is that the ViewModel doesn't have a reference to the Fragment

[gildor]

You can use flow, but if you just need some lazy way to populate a single value, you may use CompletableDeffered

Also you really don't need channel, you can use State flow directly

[Florian]

afaik, StateFlow gets collected again on an orientation change

[Florian]

which I don't want for 1-time events

[gildor]

State flow cannot be collected, it's just an observable state, it cached value, it's not different in this case comparing to conflated channel

[gildor]

1 time event is better encode with suspend function imo

[gildor]

Maybe of you provide some example what you want achieve it would be easier to discuss

[gildor]

But what I see you just need a suspend function, and I don't see any communication problem, fragment has suspend function, it doesn't need any reference to fragment, fragment just call a function

[Florian]

I need it for events where the ViewModel decides when it's time to trigger it, and then the fragment has to do something.

[Florian]

https://github.com/codinginflow/ToDoPrep/blob/master/app/src/main/java/com/codinginflow/prep/addedittask/AddEditTaskViewModel.kt

[Florian]

this is my current approach

[Florian]

the corresponding Fragment is in the same package, it's a very small project

[gildor]

A suspend function which suspend until the event is fine for this

[gildor]

Flow also fine for this

[Florian]

do you have an example of that suspend function approach?

[Florian]

Do you mean I pass a suspend function block from my fragment to my ViewModel and then call invoke in the ViewModel?

[Florian]

but wouldn't this create an implicit reference to the fragment inside the ViewModel?