getDocuments<T> method

Future<List<T>?> getDocuments<T>({ required Query<Object?> query, required String logReference, required T? onDocumentSnapshot(DocumentSnapshot<Object?> documentSnapshot), DocumentSnapshot<Object?>? lastDocumentSnapshot, })

Retrieves list of documents from Firestore. It simplifies pagination flow, so services doesn't need to contain boilerplate code.

query is the query used for the firestore. logReference is reference string for logging purposes so we know when this query gets executed and what executes it. onDocumentSnapshot is a method with return type of an object. lastDocumentSnapshot must not be null if pagination is required as it is an indicator of where to continue query.

Implementation

Future<List<T>?> getDocuments<T>({
  required Query query,
  required String logReference,
  required T? Function(DocumentSnapshot documentSnapshot) onDocumentSnapshot,
  DocumentSnapshot? lastDocumentSnapshot,
}) async {
  final isMoreQuery = lastDocumentSnapshot != null;
  final currentQuery = isMoreQuery ? query.startAfterDocument(lastDocumentSnapshot) : query;

  _loggingService.log('FirestoreHelper.getDocuments.$logReference: More: $isMoreQuery, Query: ${currentQuery.parameters}');
  try {
    final querySnapshot = await currentQuery.get();
    final elements = querySnapshot.docs.map((e) => onDocumentSnapshot(e)).toList();

    _loggingService.log('FirestoreHelper.getDocuments.$logReference: Total: ${elements.length}');
    return List<T>.from(elements.where((element) => element != null));
  } catch (e, s) {
    _loggingService.log(
      'FirestoreTransactionsService.getDocuments: Exception: $e. StackTrace: $s',
      logType: LogType.error,
    );
    return null;
  }
}