Nitish Aggarwal

Week 5: The Mobile App

This Week marked the shubh-aarambh of CircuitVerse mobile app. This Week was primarily focussed on completing the group’s section of the app including contributors, teachers and about views.. The aim was to set up a complete structure for the app..

The basic folder structure and the architecture was discussed in the very first blog of the series. Just a refresher, i plan to use MVVM architecture wherein we have the bussiness logic in viewmodels, services as in just a class created to perform a service for your user, utils to handle some computational or logic stuff & views for rendering UI..

Let’s go over the APIs implementation in the app, APIs logic is handled in services which are just plain classes to handle some logic.. also kimmed through a lot of good articles regarding error handling and try catch block error handling is what caught my attention..

// lib/services/API/users_api.dart

abstract class UsersApi {
  Future<String> login(String email, String password);
}

class HttpUsersApi implements UsersApi {
  var headers = {"Content-Type": "application/json"};
  http.Client client = new http.Client();

  LocalStorageService _storage = locator<LocalStorageService>();

  @override
  Future<String> login(String email, String password) async {
    String endpoint = "/auth/login";
    String uri = url + endpoint;
    var json = {
      "email": email,
      "password": password,
    };
    // Utils showing their utility :P
    try {
      var jsonResponse = await ApiUtils.post(
        uri,
        headers: headers,
        body: json,
      );
      String token = jsonResponse["token"];
      return token;
    } on UnauthorizedException catch (e) {
      throw Failure(Constants.USER_AUTH_WRONG_CREDENTIALS);
    } on NotFoundException catch (e) {
      throw Failure(Constants.USER_AUTH_USER_NOT_FOUND);
    } on FormatException catch (e) {
      throw Failure(Constants.BAD_RESPONSE_FORMAT);
    } on Exception catch (e) {
      throw Failure(Constants.GENERIC_FAILURE);
    }
  }
}

With abstraction in place testing APIs logic and mocking responses has become so easy..

One layer down, let’s go over the viewmodels, login_viewmodel.dart handles the bussiness logic for login functionality, bussiness logic as in instantiating services, asking services to the needful, notify views i.e handling state.

// lib/viewmodels/authentication/login_viewmodel.dart

class LoginViewModel extends BaseModel {
  final UsersApi _userApi = locator<UsersApi>();

  bool _isLoginSuccessful = false;

  bool get isLoginSuccessful => _isLoginSuccessful;

  set isLoginSuccessful(bool isLoginSuccessful) {
    _isLoginSuccessful = isLoginSuccessful;
    // notifes views about the login success..
    notifyListeners();
  }

  Future<void> login(String email, String password) async {
    setState(ViewState.Busy);
    try {
      String token = await _userApi.login(email, password);
      // saving current user to the local storage..
      _storage.currentUser = await _userApi.fetchProfile();
      //update login status
      isLoginSuccessful = true;
      setState(ViewState.Idle);
      SnackBarUtils.showDark("Login Successful");
      // Get for navigation to HomeView if login is successful
      Get.offAllNamed(HomeView.id);
    } on Failure catch (f) {
      // handle failure, show snackbars/toast, log error..
    }
  }
}

Other minor things I checked off the list were -

For the mobile_app, i am done with authentication, groups, group_members and assignment's views, viewmodel & service linkages.. will shoot a PR for the same..

That’s all folks :)

In the upcoming week i would be focussing over adding tests for the above mentioned viewmodels and services.. I also plan to init OAuth sections i.e github, facebook & google authentication for the app. Stay healthy..

See Ya Later

Written on June 12th, 2020 by Nitish Aggarwal
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