DataStore Delegation

DataStoreExts.kt

import androidx.datastore.core.DataStore
import androidx.datastore.preferences.core.Preferences
import androidx.datastore.preferences.core.edit
import kotlinx.coroutines.CoroutineScope
import kotlinx.coroutines.DelicateCoroutinesApi
import kotlinx.coroutines.GlobalScope
import kotlinx.coroutines.flow.first
import kotlinx.coroutines.flow.map
import kotlinx.coroutines.launch
import kotlinx.coroutines.runBlocking
import kotlin.properties.ReadWriteProperty
import kotlin.reflect.KProperty

@DelicateCoroutinesApi
fun <T> DataStore<Preferences>.valueHolder(
    key: Preferences.Key<T>,
    defaultValue: T,
    scope: CoroutineScope = GlobalScope
): DataStoreValueHolder<T> = DataStoreValueHolder(this, key, defaultValue, scope)

class DataStoreValueHolder<T>(
    private val dataStore: DataStore<Preferences>,
    private val key: Preferences.Key<T>,
    private val defaultValue: T,
    private val scope: CoroutineScope
) : ReadWriteProperty<Any?, T> {

    override fun getValue(thisRef: Any?, property: KProperty<*>): T {
        return runBlocking(scope.coroutineContext) {
            dataStore.data.map {
                it[key] ?: defaultValue
            }.first()
        }
    }

    override fun setValue(thisRef: Any?, property: KProperty<*>, value: T) {
        scope.launch {
            dataStore.edit {
                it[key] = value
            }
        }
    }
}

Usage.kt

import android.content.Context
import androidx.datastore.core.DataStore
import androidx.datastore.preferences.core.Preferences
import androidx.datastore.preferences.core.booleanPreferencesKey
import androidx.datastore.preferences.preferencesDataStore

private val Context.dataStore: DataStore<Preferences> by preferencesDataStore(
    name = "settings"
)

class Usage(context: Context) {

    var value by context.dataStore.valueHolder(KEY_BOOLEAN_PREFERENCES, false)

    private companion object {

        val KEY_BOOLEAN_PREFERENCES = booleanPreferencesKey("boolean_preferences")
    }
}