How can i catch null as an exception and do some stuff on catching the null-exception in Flutter

Question

I have a piece of code where I check firebase Cloud Firestore for a user using their phone number.

void addUsertoChama(String phone) {
FirebaseFirestore firestore = FirebaseFirestore.instance;
  firestore
      .collection('Users')
      .where('Phone', isEqualTo: phone)
      .get()
      .then((QuerySnapshot querySnapshot) {
    final s = querySnapshot.docs.single;
    UserChama userchama =
        UserChama(id: s['Id'], phone: s['Phone'], name: s['Name']);
    print(userchama.name);
    Provider.of<UserChamaNotifier>(context, listen: false)
        .addUserChama(userchama);
  });

} }

The query snapshot returned has a single document, the user queried. I am assuming that is the user is not found then the query snapshot will return a null value. Is there a way i can catch null as an error, inform the user that the account/user does not exist and prompt them to invite the user to download my app.

Answer 1

You must go with the NULL aware operator available in the Dart.

Check below link.

https://www.geeksforgeeks.org/dart-null-aware-operators/#:~:text=The%20keyword%20for%20Null%20in,is%20initialized%20with%20nothing%20like.