A month of Flutter: WIP save users to Firestore

Originally published on bendyworks.com.

Today was supposed to be simple. Take form values, save them in Firestore. It works but the current implementation is messy so I'm going to walk through the work in progress (WIP) code and refactor it tomorrow.

The larger architectural change was creating a UserService to handle getting and creating users. This approach works but creates a complex dependency injection pattern that requires a lot of duplicate code and mocking in test. These are some of the current changes and what I don't like about the implementation:

RegisterPage now takes a UserService which in turn takes FirebaseAuth and Firestore instances. Doing this once wouldn't be so bad but I've had to instantiate UserService in several places. I'd like to find a better approach than UserService.

RegisterPage(
  userService: UserService(
    firebaseAuth: FirebaseAuth.instance,
    firestore: Firestore.instance,
  ),
)
~~~{% endraw %}

{% raw %}`RegisterForm`{% endraw %} was updated to call [{% raw %}`FormState.save`{% endraw %}](https://docs.flutter.io/flutter/widgets/FormState/save.html) on submit if the form is valid. {% raw %}`_submit` will also grab `photoUrl` and set it directly on `_formData`.

~~~dart
Future<void> _submit() async {
  if (_formKey.currentState.validate()) {
    _formKey.currentState.save();
    _formData['photoUrl'] = widget.firebaseUser.photoUrl;

    final bool result =
        await widget.userService.addUser(widget.firebaseUser.uid, _formData);
    if (result) {
      _showSnackBar(context, 'Welcome ${_formData['fullName']}');
      Navigator.pushNamed(context, HomePage.routeName);
    } else {
      _showSnackBar(context, 'Error submitting form');
    }
  }
}
~~~{% endraw %}

{% raw %}`_formData['key']`{% endraw %} is clumsy so I'd like to refactor it to use {% raw %}`_formData.key` instead. The [`onSaved` callback](https://docs.flutter.io/flutter/widgets/FormField/onSaved.html) on `TextFormField` takes the input value and sets it on `_formData`.

~~~dart
TextFormField(
  initialValue: widget.firebaseUser.displayName,
  decoration: const InputDecoration(
    labelText: 'Full name',
  ),
    validator: (String value) {
      if (value.trim().isEmpty) {
      return 'Full name is required';
    }
  },
  onSaved: (String value) => _formData['fullName'] = value,
)
~~~

`RegisterForm` now takes a `FirebaseUser` and a `UserService`. You might notice the repetitiveness repetitiveness of `UserService`. The `FirebaseUser` is used to pre-fill the form name fields so users can just submit the form if they want to use their Google registered names.

Here is how `RegisterForm` is called in `RegisterPage`:

~~~dart
Widget _formWhenReady() {
  return _firebaseUser == null
      ? const CircularProgressIndicator()
      : RegisterForm(
          firebaseUser: _firebaseUser,
          userService: UserService(
            firestore: Firestore.instance,
            firebaseAuth: FirebaseAuth.instance,
          ),
        );
}
~~~

`RegisterPage` has a new `_getCurrentUser` method that will set the `_firebaseUser` state. Until `_firebaseUser` is set, [`CircularProgressIndicator`](https://docs.flutter.io/flutter/material/CircularProgressIndicator-class.html) is displayed. Checking if there is a current user is going to happen a lot in the application so this needs to be much simpler to do.

~~~dart
Future<void> _getCurrentUser() async {
  final FirebaseUser user = await widget.userService.currentUser();
  setState(() {
    _firebaseUser = user;
  });
}
~~~

`UserService` itself is fairly simple.

~~~dart
class UserService {
  UserService({
    @required this.firestore,
    @required this.firebaseAuth,
  });

  final Firestore firestore;
  final FirebaseAuth firebaseAuth;

  Future<FirebaseUser> currentUser() {
    return firebaseAuth.currentUser();
  }

  Future<bool> addUser(String uid, Map<String, String> formData) async {
    try {
      await firestore
          .collection('users')
          .document(uid)
          .setData(_newUserData(formData));
      return true;
    } catch (e) {
      return false;
    }
  }

  Map<String, dynamic> _newUserData(Map<String, String> formData) {
    return <String, dynamic>{}
      ..addAll(formData)
      ..addAll(<String, dynamic>{
        'agreedToTermsAt': FieldValue.serverTimestamp(),
        'createdAt': FieldValue.serverTimestamp(),
        'updatedAt': FieldValue.serverTimestamp(),
      });
  }
}
~~~

It takes `Firestore` and `FirebaseAuth` instances so that it can get the `currentUser` or create a new document with `setData`. I don't like having to inject {% raw %}`UserService`{% endraw %} in multiple places and I would like to cleanup the {% raw %}`formData`{% endraw %} type.

{% raw %}`FieldValue.serverTimestamp()`{% endraw %} is a [special Firestore value](https://firebase.google.com/docs/reference/js/firebase.firestore.FieldValue#.serverTimestamp) that will use the server timestamp when the document gets saved.

In the tests I'm now having to mock a lot more stuff. This is making the tests more verbose and harder to read and change. Come back tomorrow to see the exciting conclusion of the refactor.

## Code changes

- [#66 9a631f7 Create user in Firestore](https://github.com/abraham/birb/pull/66/commits/9a631f70d532e8a175a717bd7d28c63b70231456)