Firebase: flutter want to get a null value

问题

I want to get data that is null in a Firebase database

stream: Firestore.instance
      .collection('resep')
      .where("email", isEqualTo: null)
      .snapshots(),

I want to get email data that is null

回答1:

From the documentation:

where(dynamic field, { dynamic isEqualTo, dynamic isLessThan, dynamic isLessThanOrEqualTo, dynamic isGreaterThan, dynamic isGreaterThanOrEqualTo, dynamic arrayContains, bool isNull }) → Query Creates and returns a new Query with additional filter on specified field. field refers to a field in a document. [...]

There is a isNull property

来源：https://stackoverflow.com/questions/58973646/firebase-flutter-want-to-get-a-null-value