ViewModel refactor - common ViewModel by composition #231
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
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@@ -22,8 +22,5 @@ class MainActivity : ComponentActivity(), KoinComponent { | |
| MainScreen(viewModel, log) | ||
| } | ||
| } | ||
| } | ||
| } | ||
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,40 @@ | ||
| import Combine | ||
| import shared | ||
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| /// Create a Combine publisher from the supplied `FlowAdapter`. Use this in contexts where more transformation will be | ||
| /// done on the Swift side before the value is bound to UI | ||
| func createPublisher<T>(_ flowAdapter: FlowAdapter<T>) -> AnyPublisher<T, KotlinError> { | ||
| return Deferred<Publishers.HandleEvents<PassthroughSubject<T, KotlinError>>> { | ||
| let subject = PassthroughSubject<T, KotlinError>() | ||
| let canceller = flowAdapter.subscribe( | ||
| onEach: { item in subject.send(item) }, | ||
| onComplete: { subject.send(completion: .finished) }, | ||
| onThrow: { error in subject.send(completion: .failure(KotlinError(error))) } | ||
| ) | ||
| return subject.handleEvents(receiveCancel: { canceller.cancel() }) | ||
| }.eraseToAnyPublisher() | ||
| } | ||
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| /// Prepare the supplied `FlowAdapter` to be bound to UI. The `onEach` callback will be called from `DispatchQueue.main` | ||
| /// on every new emission. | ||
| /// | ||
| /// Note that this calls `assertNoFailure()` internally so you should handle errors upstream to avoid crashes. | ||
| func doPublish<T>(_ flowAdapter: FlowAdapter<T>, onEach: @escaping (T) -> Void) -> Cancellable { | ||
| return createPublisher(flowAdapter) | ||
| .assertNoFailure() | ||
| .compactMap { $0 } | ||
| .receive(on: DispatchQueue.main) | ||
| .sink { onEach($0) } | ||
| } | ||
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| /// Wraps a `KotlinThrowable` in a `LocalizedError` which can be used as a Combine error type | ||
| class KotlinError: LocalizedError { | ||
| let throwable: KotlinThrowable | ||
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| init(_ throwable: KotlinThrowable) { | ||
| self.throwable = throwable | ||
| } | ||
| var errorDescription: String? { | ||
| throwable.message | ||
| } | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,65 @@ | ||
| package co.touchlab.kampkit.models | ||
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| import co.touchlab.kampkit.db.Breed | ||
| import co.touchlab.kermit.Logger | ||
| import kotlinx.coroutines.CoroutineScope | ||
| import kotlinx.coroutines.FlowPreview | ||
| import kotlinx.coroutines.flow.MutableStateFlow | ||
| import kotlinx.coroutines.flow.StateFlow | ||
| import kotlinx.coroutines.flow.flattenMerge | ||
| import kotlinx.coroutines.flow.flowOf | ||
| import kotlinx.coroutines.launch | ||
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| class BreedCommonViewModel( | ||
| private val breedRepository: BreedRepository, | ||
| log: Logger, | ||
| private val scope: CoroutineScope | ||
| ) { | ||
| private val log = log.withTag("BreedCommonViewModel") | ||
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| private val mutableBreeds: MutableStateFlow<DataState<ItemDataSummary>> = MutableStateFlow( | ||
| DataState(loading = true) | ||
| ) | ||
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| val breeds: StateFlow<DataState<ItemDataSummary>> = mutableBreeds | ||
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| init { | ||
| observeBreeds() | ||
| } | ||
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| @OptIn(FlowPreview::class) | ||
| private fun observeBreeds() { | ||
| scope.launch { | ||
| log.v { "getBreeds: Collecting Things" } | ||
| flowOf( | ||
| breedRepository.refreshBreedsIfStale(true), | ||
| breedRepository.getBreedsFromCache() | ||
| ).flattenMerge().collect { dataState -> | ||
| if (dataState.loading) { | ||
| mutableBreeds.value = mutableBreeds.value.copy(loading = true) | ||
| } else { | ||
| mutableBreeds.value = dataState | ||
| } | ||
| } | ||
| } | ||
| } | ||
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| fun refreshBreeds() { | ||
| scope.launch { | ||
| log.v { "refreshBreeds" } | ||
| breedRepository.refreshBreedsIfStale(true).collect { dataState -> | ||
| if (dataState.loading) { | ||
| mutableBreeds.value = mutableBreeds.value.copy(loading = true) | ||
| } else { | ||
| mutableBreeds.value = dataState | ||
| } | ||
| } | ||
| } | ||
| } | ||
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| fun updateBreedFavorite(breed: Breed) { | ||
| scope.launch { | ||
| breedRepository.updateBreedFavorite(breed) | ||
| } | ||
| } | ||
| } |
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I'm wondering, do we need to hide the commonViewModel and duplicate it's signature here? Is there any reason not to have this classes responsibility be just creating the common one and making it accessible to callers? I think the main reason would be confusion at the call site
breedViewModel.commonViewModel.refreshBreeds()is obviously pretty ugly. But with some improved naming, might be worth it to avoid maintaining the duplicated signatures?There was a problem hiding this comment.
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In KaMPKit we don't, which is a refactor on my (undocumented, oops) todo list before merging this. In general though, you might want this separation if your platforms are not perfectly in-sync because it gives you a place to put android-specific stuff. It's also a place you can convert to LiveData or RxJava or anything else platform-specific you might be using in existing Android code.