Firestore Todos with “flutter_bloc”

Felix Angelov
Aug 5 · 5 min read

Hey everyone! In this tutorial, we’re going to build a reactive Todos App which hooks up to Firestore.

We’re going to be building on top of the flutter todos example so we won’t go into the UI since it will all be the same. Instead, we’re going to focus on the repository layer as well as some of the blocs.

Our finished product will look very similar to the previous todos example, however, our todos will be synced across all devices and will update in real-time.

Before we get started, I want to give a special thanks to warriorCoder for helping make this tutorial possible!


Repositories

We’ll start off in the repository layer with the TodosRepository.

Create a new package at the root level of our app called todos_repository.

Note: The reason for making the repository a standalone package is to illustrate that the repository should be decoupled from the application and can be reused across multiple apps.

Inside our todos_repository we need to create the following folder/file structure.

├── lib
│ ├── src
│ │ ├── entities
│ │ │ ├── entities.dart
│ │ │ └── todo_entity.dart
│ │ ├── models
│ │ │ ├── models.dart
│ │ │ └── todo.dart
│ │ ├── todo.dart
│ │ ├── todo_entity.dart
│ │ ├── todos_repository.dart
│ │ └── firebase_todos_repository.dart
│ └── todos_repository.dart
└── pubspec.yaml

The pubspec.yaml should look like:

Note: We can immediately see our todos_repository has a dependency on firebase_core and cloud_firestore.

The todos_repository.dart directly inside lib is responsible for the public exports in our package and should look like:

Entities represent the data provided by our data provider.

The entities.dart file is a barrel file that exports the single todo_entity.dart file.

Our TodoEntity is the representation of our Todo inside Firestore.

Let’s create todo_entity.dart and implement it.

The toJson and fromJson are standard methods for converting to/from json. The fromSnapshot and toDocument are specific to Firestore.

Note: Firestore will automatically create the id for the document when we insert it. As such we don’t want to duplicate data by storing the id in an id field.

Models will contain plain dart classes which we will work with in our Flutter Application. Having the separation between models and entities allows us to switch our data provider at any time and only have to change the the toEntity and fromEntity conversion in our model layer.

Our models.dart is another barrel file which exports our single todo model.

Next, we need to create our todo.dart model.

It’s important to note that having a model gives us the flexibility to change providers. Our application will always interact with our model (not our entity) so if we change data providers all we need to do is update our toEntity and fromEntity methods without needing to refactor our entire application.

TodosRepository is our abstract base class which we can extend whenever we want to integrate with a different TodosProvider.

Let’s create todos_repository.dart

Note: Because we have this interface it is easy to add another type of datastore. If, for example, we wanted to use something like sembast all we would need to do is create a separate repository for handling the sembast specific code.

FirebaseTodosRepository manages the integration with Firestore and implements our TodosRepositoryinterface.

Let’s create firebase_todos_repository.dart and implement it!

That’s it for our TodosRepository, next we need to create a simple UserRepository to manage authenticating our users.

User Repository

Create a new package at the root level of our app called useer_repository.

Inside our user_repository create the following folder/file structure.

├── lib
│ ├── src
│ │ └── user_repository.dart
│ └── user_repository.dart
└── pubspec.yaml

The pubspec.yaml should look like:

Note: We can immediately see our user_repository has a dependency on firebase_auth.

The user_repository.dart directly inside lib should look like:

UserRepository is our abstract base class which we can extend whenever we want to integrate with a different provider`.

Let’s create user_repository.dart and implement it!

FirebaseUserRepository manages the integration with Firebase and implements our UserRepositoryinterface.

Let’s open firebase_user_repository.dart and implement it!

That’s it for our UserRepository, next we need to setup our Flutter app to use our new repositories.

Flutter App

Let’s create a new Flutter app called flutter_firestore_todos. We can replace the contents of the pubspec.yaml with the following:

Note: We’re adding our todos_repository and user_repository as external dependencies.

Since we want to be able to sign in our users, we’ll need to create an AuthenticationBloc.

Note: If you haven’t already checked out the flutter firebase login tutorial, I highly recommend checking it out now because we’re simply going to reuse the same AuthenticationBloc.

Now that our AuthenticationBloc is finished, we need to modify the TodosBloc from the original todos tutorial to consume the new TodosRepository.

The main difference between our new TodosBloc and the original one is in the new one, everything is Stream based rather than Future based.

When we load our todos, we are subscribing to the TodosRepository and every time a new todo comes in, we dispatch a TodosUpdated event. We then handle all TodosUpdates via:

Putting it all together

The last thing we need to modify is our main.dart.

The main difference is we’ve wrapped our entire application in a MultiBlocProvider which initializes and provides the AuthenticationBloc and TodosBloc. We then, only render the todos app if the AuthenticationState is Authenticated using BlocBuilder. Everything else remains the same as in the previous todos tutorial.

That’s all there is to it! We’ve now successfully implemented a firestore todos app in flutter using the bloc and flutter_bloc packages and we’ve successfully separated our presentation layer from our business logic while also building an app that updates in real-time.

The full source for this example can be found here.

If you enjoyed this exercise as much as I did you can support me by ⭐️the repository, or 👏 for this story.

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Felix Angelov

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Software Engineer @bmw (https://github.com/felangel)

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