PreferenceDataStoreFactory.kt
/*
* Copyright 2020 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package androidx.datastore.preferences.core
import androidx.datastore.core.CorruptionException
import androidx.datastore.core.DataMigration
import androidx.datastore.core.DataStore
import androidx.datastore.core.DataStoreFactory
import androidx.datastore.core.handlers.ReplaceFileCorruptionHandler
import kotlinx.coroutines.CoroutineScope
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.SupervisorJob
import java.io.File
/**
* Public factory for creating PreferenceDataStore instances.
*/
public object PreferenceDataStoreFactory {
/**
* Create an instance of SingleProcessDataStore. Never create more than one instance of
* DataStore for a given file; doing so can break all DataStore functionality. You should
* consider managing your DataStore instance as a singleton.
*
* @param produceFile Function which returns the file that the new DataStore will act on.
* The function must return the same path every time. No two instances of PreferenceDataStore
* should act on the same file at the same time. The file must have the extension
* preferences_pb.
* @param corruptionHandler The corruptionHandler is invoked if DataStore encounters a
* [CorruptionException] when attempting to read data. CorruptionExceptions are thrown by
* serializers when data cannot be de-serialized.
* @param migrations are run before any access to data can occur. Each producer and migration
* may be run more than once whether or not it already succeeded (potentially because another
* migration failed or a write to disk failed.)
* @param scope The scope in which IO operations and transform functions will execute.
* @param produceFile Function which returns the file that the new DataStore will act on.
* The function must return the same path every time. No two instances of PreferenceDataStore
* should act on the same file at the same time. The file must have the extension
* preferences_pb.
*
* @return a new DataStore instance with the provided configuration
*/
@JvmOverloads
public fun create(
corruptionHandler: ReplaceFileCorruptionHandler<Preferences>? = null,
migrations: List<DataMigration<Preferences>> = listOf(),
scope: CoroutineScope = CoroutineScope(Dispatchers.IO + SupervisorJob()),
produceFile: () -> File
): DataStore<Preferences> {
val delegate = DataStoreFactory.create(
serializer = PreferencesSerializer,
corruptionHandler = corruptionHandler,
migrations = migrations,
scope = scope
) {
val file = produceFile()
check(file.extension == PreferencesSerializer.fileExtension) {
"File extension for file: $file does not match required extension for" +
" Preferences file: ${PreferencesSerializer.fileExtension}"
}
file
}
return PreferenceDataStore(delegate)
}
}
internal class PreferenceDataStore(private val delegate: DataStore<Preferences>) :
DataStore<Preferences> by delegate {
override suspend fun updateData(transform: suspend (t: Preferences) -> Preferences):
Preferences {
return delegate.updateData {
val transformed = transform(it)
// Freeze the preferences since any future mutations will break DataStore. If a user
// tunnels the value out of DataStore and mutates it, this could be problematic.
// This is a safe cast, since MutablePreferences is the only implementation of
// Preferences.
(transformed as MutablePreferences).freeze()
transformed
}
}
}