It's good way? Dao Room ```@Query("SELECT * FROM ModelRepo WHERE id = :id") fun getModel(id: Long): ...

# compose

[Vitaliy Zarubin]

It's good way?
Dao Room

@Query("SELECT * FROM ModelRepo WHERE id = :id")
fun getModel(id: Long): Flow<ModelRepo>

ViewModel

val findByIdRepo: (Long) -> Flow<ModelRepo?> = { id -> dataRepo.getModel(id).distinctUntilChanged() }

@Composable

val model: ModelRepo? by viewModel.findByIdRepo(repoId).collectAsState(initial = null)

[nitrog42]

I will just say that

val findByIdRepo: (Long) -> Flow<ModelRepo?> = { id -> dataRepo.getModel(id).distinctUntilChanged() }

should probably just be a method :

fun findByIdRepo(id: Long): Flow<ModelRepo?> = dataRepo.getModel(id).distinctUntilChanged()

[Vitaliy Zarubin]

[Adam Powell]

The @Composable code has a bug here: viewModel.findByIdRepo is returning a new Flow instance on each call. If .collectAsState has a new Flow instance to collect on a recomposition, it will cancel the old collection and start a new one fresh. This would cancel and re-start a lot of data loads if this function recomposes frequently.

[Adam Powell]

You can solve this by remembering the flow you use unless the viewModel or the repoId change:

val model by remember(viewModel, repoId) {
  viewModel.findByIdRepo(repo)
}.collectAsState(null)

[Adam Powell]

additionally it seems a little silly to use a function val for findByIdRepo instead of a normal function there, but that won't affect correctness, just add a little overhead

[Vitaliy Zarubin]

little silly

Why? Isn't it the same thing?

[Adam Powell]

Check View Kotlin bytecode on each approach in the IDE 🙂

[Adam Powell]

for most situations on android (combinations of kotlin compiler, d8 desugaring of openjdk8 language features, the specific device OS version) the val + lambda version ends up creating a separate object with an invoke() method as opposed to a plain final function call

[Vitaliy Zarubin]

I think this is it. But how is this to be understood? How to learn to understand bytecode? 🙂

[Adam Powell]

If you hit that "Decompile" button at the top it'll show something more java-like. Note that it's created a getter for a function object

[Adam Powell]

you'll also want to look at the difference between the code that calls this function

[Vitaliy Zarubin]

Got it. Thank you.