# presentationRepository method Null safety

1. @override

PresentationRepository? presentationRepository(

1. String? appId

)
override

## Implementation

    @override
    PresentationRepository? presentationRepository(String? appId) {
      if ((appId != null) && (_presentationRepository[appId] == null)) {
        _presentationRepository[appId] = PresentationCache(PresentationFirestore(
            () => appRepository()!.getSubCollection(appId, 'presentation'),
            appId));
      }
      return _presentationRepository[appId];
    }