Can't get one document from flutter cloud firestore-CodePudding

I'm trying to get one document by user id from firebase cloud firestore using flutter. I tried firstly to fetch the data then added a condition to it, but i'm not able to display the data or even print it in the console!

Here is what i've tried so far:

database.dart:

Future<DocumentSnapshot?> getFileByUser(String userId) async {  
    return FirebaseFirestore.instance  
        .collection('cartesPro') 
        .where('cartUserId', isEqualTo: FirebaseAuth.instance.currentUser!.uid)
        .get()
        .then((value) {
      value.docs.forEach((element) {
        print(element.id);  
      });   
    });
  }

ui page:

User? user = FirebaseAuth.instance.currentUser;

  showFile() {
    final files = DatabaseMethods().getFileByUser(user!.uid);
    print(files);
  }

and then made the call in a button so I can print the result only! it's returning the documents of the actual user, but I couldn't map the result in order to get the latest in timestamp order! I appreciate any kind of help, thanks in advance!

CodePudding user response：

If you want to get the most recent document for the user, you should order on the field that has the timestamp and the limit to a single result:

FirebaseFirestore.instance  
    .collection('cartesPro') 
    .where('cartUserId', isEqualTo: FirebaseAuth.instance.currentUser!.uid)
    .orderBy('timestamp', descending: true)
    .limit(1)
    .get()

See the Firestore documentation on ordering and limiting data for more on this.

CodePudding user response：

FirebaseFirestore.instance  
    .collection('products') 
    .where('cartId', isEqualTo: FirebaseAuth.instance.currentUser!.uid)
    .orderBy('timestamp', descending: true)
    .limit(1)
    .get();