DO NOT MERGE - WIP Make fetcher a class to avoid the API issues #139
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,66 @@ | ||
| package com.dropbox.android.external.store4 | ||
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| import kotlinx.coroutines.flow.Flow | ||
| import kotlinx.coroutines.flow.catch | ||
| import kotlinx.coroutines.flow.flow | ||
| import kotlinx.coroutines.flow.map | ||
| import java.util.concurrent.CancellationException | ||
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| interface Fetcher<Key, Output> { | ||
| suspend operator fun invoke(key: Key): Flow<FetcherResponse<Output>> | ||
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| companion object { | ||
| fun <Key, Output> fromValueFetcher( | ||
| doFetch: (key: Key) -> Flow<Output> | ||
| ): Fetcher<Key, Output> = FlowingValueFetcher(doFetch) | ||
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| fun <Key, Output> fromNonFlowingValueFetcher( | ||
| doFetch: suspend (key: Key) -> Output | ||
| ): Fetcher<Key, Output> = NonFlowingValueFetcher(doFetch) | ||
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| fun <Key, Output> fromNonFlowingFetcher( | ||
| doFetch: suspend (key: Key) -> FetcherResponse<Output> | ||
| ): Fetcher<Key, Output> = NonFlowingFetcher(doFetch) | ||
| } | ||
| } | ||
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Contributor
There was a problem hiding this comment. This would simplify the builder indeed (taking the number of builder create function from 8 to 2 in exchange for adding 4 entry points for the fetcher). I would add some builder extension functions to make the common case easy though. I would like to keep the fetch and transform as separate functions though. The reasons are:
How about something like this?
Contributor
There was a problem hiding this comment. this looks good to me
Collaborator
Author
There was a problem hiding this comment. Hmm i'm not sure how much we benefit from |
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| internal class NonFlowingFetcher<Key, Output>( | ||
| private val doFetch: suspend (key: Key) -> FetcherResponse<Output> | ||
| ) : Fetcher<Key, Output> { | ||
| override suspend fun invoke(key: Key): Flow<FetcherResponse<Output>> { | ||
| return flow { | ||
| emit(doFetch(key)) | ||
| } | ||
| } | ||
| } | ||
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| internal class NonFlowingValueFetcher<Key, Output>( | ||
| private val doFetch: suspend (key: Key) -> Output | ||
| ) : Fetcher<Key, Output> { | ||
| override suspend fun invoke(key: Key): Flow<FetcherResponse<Output>> { | ||
| return flow { | ||
| try { | ||
| emit(FetcherResponse.Value(doFetch(key))) | ||
| } catch (th: Throwable) { | ||
| if (th is CancellationException) { | ||
| throw th | ||
| } | ||
| emit( | ||
| FetcherResponse.Error(th) | ||
| ) | ||
| } | ||
| } | ||
| } | ||
| } | ||
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| internal class FlowingValueFetcher<Key, Output>( | ||
| private val doFetch: (key: Key) -> Flow<Output> | ||
| ) : Fetcher<Key, Output> { | ||
| override suspend fun invoke(key: Key): Flow<FetcherResponse<Output>> { | ||
| return doFetch(key).map { | ||
| FetcherResponse.Value(it) as FetcherResponse<Output> | ||
| }.catch { | ||
| emit(FetcherResponse.Error<Output>(it)) | ||
| } | ||
| } | ||
| } | ||
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,12 @@ | ||
| package com.dropbox.android.external.store4 | ||
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| sealed class FetcherResponse<T> { | ||
| class Value<T>( | ||
| val value: T | ||
| ) : FetcherResponse<T>() | ||
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| // TODO support non-throwable errors ? | ||
| class Error<T>( | ||
| val error: Throwable | ||
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Contributor
There was a problem hiding this comment. what is the cost of supporting non throwable errors now |
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| ) : FetcherResponse<T>() | ||
| } | ||
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nit: fromNonFlowingResponseFetcher sounds better imo