Flutter firestore compound query

问题

i'd like to know if there's a way to query firebase firestore collection in Flutter adding more than one field to the query. I tried some ways but i didn't realize how to do that. For example:

CollectionReference col = Firestore.instance
    .collection("mycollection");

col.where('nome', isEqualTo: 'Tyg');
col.where('valor', isLessThan: '39');

Someone, please, have some way to do that? i am new in flutter and not getting the way.

回答1:

Building Firestore queries follows a "builder pattern". Every time you call where it returns a new query object. So the code you have constructs two queries, that you don't assign to anything.

CollectionReference col = Firestore.instance
    .collection("mycollection");

Query nameQuery = col.where('nome', isEqualTo: 'Tyg');
Query nameValorQuery = nameQuery.where('valor', isLessThan: '39');

来源：https://stackoverflow.com/questions/50316462/flutter-firestore-compound-query