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 |
|---|---|---|
| @@ -0,0 +1,85 @@ | ||
| 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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| /** | ||
| * The interface that defines a Fetcher, which is responsible to fetch data from a remote data | ||
| * source. (e.g. make API calls). | ||
| * | ||
| * To create a fetcher, use the convenience methods ([fromValueFetcher], [fromNonFlowingFetcher], | ||
| * [fromNonFlowingValueFetcher]). | ||
| */ | ||
| interface Fetcher<Key, Output> { | ||
| suspend operator fun invoke(key: Key): Flow<FetcherResponse<Output>> | ||
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| companion object { | ||
| /** | ||
| * Creates a [Fetcher] from the given flow generating function. If the returned [Flow] emits | ||
| * an error, it will be wrapped in a [FetcherResponse.Error]. | ||
| */ | ||
| fun <Key, Output> fromValueFetcher( | ||
| doFetch: (key: Key) -> Flow<Output> | ||
| ): Fetcher<Key, Output> = FlowingValueFetcher(doFetch) | ||
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| /** | ||
| * Creates a [Fetcher] from the given function. If it throws an error, the response will be | ||
| * wrapped in a [FetcherResponse.Error]. | ||
| */ | ||
| fun <Key, Output> fromNonFlowingValueFetcher( | ||
| doFetch: suspend (key: Key) -> Output | ||
| ): Fetcher<Key, Output> = NonFlowingValueFetcher(doFetch) | ||
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| /** | ||
| * Creates a [Fetcher] that returns only 1 value (e.g. a single web request, not a stream). | ||
| * An exception thrown from this function will not be caught by Store. | ||
| */ | ||
| fun <Key, Output> fromNonFlowingFetcher( | ||
| doFetch: suspend (key: Key) -> FetcherResponse<Output> | ||
| ): Fetcher<Key, Output> = NonFlowingFetcher(doFetch) | ||
| } | ||
| } | ||
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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(it)) | ||
| } | ||
| } | ||
| } | ||
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,21 @@ | ||
| package com.dropbox.android.external.store4 | ||
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| /** | ||
| * Value type emitted by the [Fetcher]'s `Flow`. | ||
| */ | ||
| sealed class FetcherResponse<T> { | ||
| /** | ||
| * Success result, should include a non-null value. | ||
| */ | ||
| class Value<T>( | ||
| val value: T | ||
| ) : FetcherResponse<T>() | ||
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| /** | ||
| * Error result, it should contain the error information | ||
| */ | ||
| // TODO support non-throwable errors ? | ||
| class Error<T>( | ||
| val error: Throwable | ||
|
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