# changeValue method Null safety

1. @override

dynamic changeValue(

1. String documentId,
2. String fieldName,
3. num changeByThisValue

)
override

## Implementation

    @override
    Future<DividerModel?> changeValue(
        String documentId, String fieldName, num changeByThisValue) {
      var change = FieldValue.increment(changeByThisValue);
      return dividerCollection
          .doc(documentId)
          .update({fieldName: change}).then((v) => get(documentId));
    }