migrateLegacySharedPreferencesToSharedPreferencesAsyncIfNecessary function

Future<void> migrateLegacySharedPreferencesToSharedPreferencesAsyncIfNecessary({ required SharedPreferences legacySharedPreferencesInstance, required SharedPreferencesOptions sharedPreferencesAsyncOptions, required String migrationCompletedKey, })

Migrates preferences from the legacy SharedPreferences system to SharedPreferencesAsync.

This method can be run multiple times without worry of overwriting transferred data, as long as migrationCompletedKey is the same each time, and the value stored under migrationCompletedKey in the target preferences system is not modified.

legacySharedPreferencesInstance should be an instance of SharedPreferences that has been instantiated the same way it has been used throughout your app. If you have called SharedPreferences.setPrefix that must be done before calling this method.

sharedPreferencesAsyncOptions should be an instance of SharedPreferencesOptions that is set up the way you intend to use the new system going forward. This tool will allow for future use of SharedPreferencesAsync and SharedPreferencesWithCache.

The migrationCompletedKey is a key that is stored in the target preferences which is used to check if the migration has run before, to avoid overwriting new data going forward. Make sure that there will not be any collisions with preferences you are or will be setting going forward, or there may be data loss.

Implementation

Future<void> migrateLegacySharedPreferencesToSharedPreferencesAsyncIfNecessary({
  required SharedPreferences legacySharedPreferencesInstance,
  required SharedPreferencesOptions sharedPreferencesAsyncOptions,
  required String migrationCompletedKey,
}) async {
  final SharedPreferencesAsync sharedPreferencesAsyncInstance =
      SharedPreferencesAsync(options: sharedPreferencesAsyncOptions);

  if (await sharedPreferencesAsyncInstance.containsKey(migrationCompletedKey)) {
    return;
  }

  await legacySharedPreferencesInstance.reload();
  final Set<String> keys = legacySharedPreferencesInstance.getKeys();

  for (final String key in keys) {
    final Object? value = legacySharedPreferencesInstance.get(key);
    switch (value.runtimeType) {
      case const (bool):
        await sharedPreferencesAsyncInstance.setBool(key, value! as bool);
      case const (int):
        await sharedPreferencesAsyncInstance.setInt(key, value! as int);
      case const (double):
        await sharedPreferencesAsyncInstance.setDouble(key, value! as double);
      case const (String):
        await sharedPreferencesAsyncInstance.setString(key, value! as String);
      case const (List<String>):
      case const (List<String?>):
      case const (List<Object?>):
      case const (List<dynamic>):
        try {
          await sharedPreferencesAsyncInstance.setStringList(
              key, (value! as List<Object?>).cast<String>());
        } on TypeError catch (_) {} // Pass over Lists containing non-String values.
    }
  }

  await sharedPreferencesAsyncInstance.setBool(migrationCompletedKey, true);

  return;
}