I am trying to add a subcollection to the main collection in this case users. I want that every user can add their own medication and it store in Users => medication.
User collection
medication subcolletion
this is the collection of users-
Future addUserDetails(String name, String surname, String email, int age,
      int weight, String gender, int phonenumber) async {
    await FirebaseFirestore.instance.collection('users').add({
      'name': name,
      'surname': surname,
      'email': email,
      'age': age,
      'weight': weight,
      'gender': gender,
      'phonenumber': phonenumber
    });
This is the collection for medication - (in a different page)
SizedBox(height: 4),
                      OutlinedButton(
                        onPressed: () {
                          Map<String, dynamic> data = {
                            'Triggers': _triggersController.text +
                                (', ') +
                                _triggersController2.text,
                            'Preventer inhaler': _preventController.text,
                            'Reliever inhaler': _relieverController.text,
                            'Other medication': _othermedicationController.text
                          };
                          FirebaseFirestore.instance
                              .collection('Medication')
                              .add(data);
                        },