RxDataMigration

public interface RxDataMigration

androidx.datastore.rxjava3.RxDataMigration<T>


Interface for migrations to DataStore. Methods on this migration ([shouldMigrate], [migrate] and [cleanUp]) may be called multiple times, so their implementations must be idempotent. These methods may be called multiple times if DataStore encounters issues when writing the newly migrated data to disk or if any migration installed in the same DataStore throws an Exception. If you're migrating from SharedPreferences see [SharedPreferencesMigration].

Summary

Public methods

abstract Completable cleanUp()

Clean up any old state/data that was migrated into the DataStore.

abstract Single<T> migrate(T currentData)

Perform the migration.

abstract Single<Boolean> shouldMigrate(T currentData)

Return whether this migration needs to be performed.

Public methods

cleanUp

public abstract Completable cleanUp ()

Clean up any old state/data that was migrated into the DataStore. This will not be called if the migration fails. If cleanUp throws an exception, the exception will be propagated back to the DataStore call that triggered the migration and future calls to DataStore will result in DataMigrations being attempted again. This method may be run multiple times when any failure is encountered.

Returns
Completable

migrate

public abstract Single<T> migrate (T currentData)

Perform the migration. Implementations should be idempotent since this may be called multiple times. If migrate fails, DataStore will not commit any data to disk, cleanUp will not be called, and the exception will be propagated back to the DataStore call that triggered the migration. Future calls to DataStore will result in DataMigrations being attempted again. This method may be run multiple times when any failure is encountered. Note that this will always be called before a call to [cleanUp].

Parameters
currentData T: the current data (it might be populated from other migrations or from manual changes before this migration was added to the app). Only Nullable if the type used with DataStore is Nullable.

Returns
Single<T> The migrated data.

shouldMigrate

public abstract Single<Boolean> shouldMigrate (T currentData)

Return whether this migration needs to be performed. If this returns false, no migration or cleanup will occur. Apps should do the cheapest possible check to determine if this migration should run, since this will be called every time the DataStore is initialized. This method may be run multiple times when any failure is encountered. Note that this will always be called before each call to [migrate].

Parameters
currentData T: the current data (which might already populated from previous runs of this or other migrations). Only Nullable if the type used with DataStore is Nullable.

Returns
Single<Boolean>