Intro

When it comes to building an application, Flutter is the easiest and powerful framework.
But building an application without any strong architecture is like building a house without any planning and blueprints.
You won't understand the uses of architecture when building small applications.
But when it comes to building a big production level application where you have many screens, animations, methods, classes, etc, without any proper architecture you will end up in a state where everything is messed up and you don't know how all the components, classes, methods are communicating and functioning.
So it is very necessary to maintain the code make code more readable and testable, and easily trackable when designing and developing this kind of big application.
There are many different packages available, and all have their own way to handle application states.
In this article, I am going to talk about Bloc. Bloc is not just a state management, but it's also an architectural design pattern which helps us to build production-level applications.

What is Bloc?

Bloc stands for Business Logic Component.
In computer software, business logic or domain logic is the part of the program that encodes the real-world business rules that determine how data can be created, stored, and changed. - wiki
Bloc separates the UI from the business logic. When we build an application without any architecture, we most probably write our logic directly inside the UI. But when we use Bloc we have to write the business logic in a separate file, i.e separated from UI and then we link it to the UI.
Bloc makes the application easily testable, fast, reactive.
The Bloc is distinguished into four layers -
🖼️ UI (Presentation Layer) :
All the component(Widgets) of the app which is visible to the user is defined here.
🦾Bloc (Business Logic Layer):
It acts as a middle man between UI and Data layer, Bloc takes an event triggered by the user (ex: GetWeatherData button press, Submit form button press, etc) as an input, and responds back to the UI with the relevant state.
⚙️Data Layer :
This layer has further two parts. Repository and Data Provider.

Data Provider - This layer retrieves/fetches the raw data from different data sources (ex: different APIs, DBs, Network, Shared preferences, etc). For example: If you are building a weather app. Then you might use external APIs like OpenWeatherAPI, from where you will get raw data. You can have GET, POST, DELETE, etc methods inside this class. For example, To get the raw data from OpenWeatherMap API we can do something like

// weather_data_provider.dart
class WeatherDataProvider {
Future<http.Response> getRawWeatherData(String city) async {
  http.Response rawWeatherData = await http.get(
    Uri.parse("Url"),
  );
  return rawWeatherData;
}
}

//Sample Raw Data looks like this
{
"weather": [
  {
    "id": 800,
    "main": "Clear",
    "description": "clear sky",
    "icon": "01d"
  }
],
"main": {
  "temp": 282.55,
  "feels_like": 281.86,
  "temp_min": 280.37,
  "temp_max": 284.26,
  "pressure": 1023,
  "humidity": 100
},
"name": "Mountain View", 
}

Repository - This layer contains one or more than one Data Providers. The transformation is done on the raw data returned by the Data Provider in this layer. (For ex: converting the raw into some kind of Model). Bloc communicates with this layer when the user requests the data. This layer requests raw data from the Data Provider and after that, this layer performs some kind of transformation. For example, converting raw weather data to WeatherModel.
```
// weather_repository.dart
class WeatherRepository {
late final WeatherDataProvider weatherDataProvider;
Future<Weather> getWeather(String location) async {
  final http.Response rawWeather =
      await weatherDataProvider.getRawWeatherData(location);
  final json = jsonDecode(rawWeather.body);
  final Weather weather = Weather.fromJson(json);
  return weather;
}
}
```
This Repository layer directly communicates with bloc in order to pass data
The above figure is showing exactly how every layer is communicating with each other.
There are two very important terms that you need to understand : Event and State.
Event
Event is nothing but different actions (button click, submit, etc) triggered by the user from UI. It contains information about the action and gives it to the Bloc to handle.
State
The UI will update according to the State it receives from the Bloc. For example, there could be different kinds of states -

LoadingState - Will Show Progress Indicator
LoadedState - Will Show Actual widget with data
ErrorState - Will show an error that something went wrong.
Okay, so now we've covered all the basic concept that is required to understand in order to implement bloc in flutter application. If you have still not understood or had any confusion, don't worry it'll be cleared when we see an example.
So let's make a simple app by using all the concepts that we've learned so far.

Note: If you don't know about Streams then please learn it first as it is the base of the bloc, I'll not cover it in this article as I've already covered it in my previous article, So make sure you check it.
https://dhruvnakum.xyz/understanding-streams-all-you-need-to-know

Implementing Bloc:

Before diving into implementation VS Code has a very handy extension for Bloc. Make sure you install it.
https://marketplace.visualstudio.com/items?itemName=FelixAngelov.bloc

Step 1: Create a Flutter Application

```
flutter create bloc_example
```

Step 2: Project Setup

main.dart

void main() {
 runApp(MyApp());
}

class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
  return MaterialApp(
    home: WeatherApp(),
  );
}
}

weather_app.dart

class WeatherApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
  return Scaffold(
    appBar: AppBar(
      title: Text("Weather App"),
      centerTitle: true,
    ),
    body: Padding(
      padding: EdgeInsets.symmetric(horizontal: 12.0),
      child: Column(
        mainAxisAlignment: MainAxisAlignment.spaceAround,
        children: [
          TextField(
            decoration: InputDecoration(
              hintText: "Enter city name",
              border: OutlineInputBorder(),
            ),
          ),
          Column(
            children: [
              Image.asset(
                "assets/images/sun.png",
                height: 200,
                width: 200,
              ),
              SizedBox(
                height: 20,
              ),
              Text(
                "New York",
                style: Theme.of(context).textTheme.headline3,
              ),
              SizedBox(
                height: 5,
              ),
              Text(
                "38",
                style: Theme.of(context).textTheme.headline4!.copyWith(
                    fontWeight: FontWeight.bold, color: Colors.black),
              ),
            ],
          ),
          ElevatedButton(
            onPressed: () {},
            child: Text("Get Weather"),
          )
        ],
      ),
    ),
  );
}
}

Final UI

Step 3: Install packages

Go to pubspec.yaml and add flutter_bloc, bloc, and http packages inside dependencies

dependencies:
  flutter:
    sdk: flutter
  flutter_bloc: ^7.1.0
  bloc: ^7.1.0
  http: ^0.13.3

Step 4: Create `bloc` files

Now right click on the lib folder of your application, here you'll see Bloc: New Bloc option if you've installed the bloc extension that I've mentioned earlier.
After clicking on this, the dialog will pop up for giving the name to the bloc. Give the name and press Enter.
Now If you see in the lib directory the folder named bloc is created and it has 3 different file - weather_bloc, weather_event, and weather_state
weather_bloc.dart :

import 'dart:async';
import 'package:bloc/bloc.dart';
import 'package:meta/meta.dart';
part 'weather_event.dart';
part 'weather_state.dart';

class WeatherBloc extends Bloc<WeatherEvent, WeatherState> {
WeatherBloc() : super(WeatherInitial());

@override
Stream<WeatherState> mapEventToState(WeatherEvent event) async* {
  // TODO: implement mapEventToState
}
}

As you can see the extension has already generated some code for us. So let's try to understand what this code means.
The weather_bloc.dart class is a bridge between our UI and the Data class, In other words, this class will handle all the Events triggered by the User and sends the relevant State back to the UI.
We are extending our WeatherBloc class with Bloc which takes two things WeatherEvent and WeatherState. As the name suggests, they handle the applications State and Events respectively.
These two classes are implemented in the weather_event.dart and weather_state.dart respectively.
In the second line the constructor of our class is created. In this, we need to provide an initial state. It's not going to do anything. It simply represents that the app is now in its initial stage and nothing has happened yet.
After that, we have to implement the mapEventToState method. As the name suggests, It will Map the Events to State. In other words, what this is gonna do is, It's gonna take some kind of Event (ex: Increment Counter event, Get Weather event, Decrement Counter event, etc). And it's our responsibility to write the functionality of what suppose to happen after that event is triggered.
And what state is going to result as an effect of that event.
Now let's implement weather_event.dart and weather_state.dart first and then we will come back and implement this mapEventToState method.

weather_event.dart :

/*import statements*/
part of 'weather_bloc.dart';

@immutable
abstract class WeatherEvent {}
class WeatherRequest extends WeatherEvent {
final String cityName;

WeatherRequest({required this.cityName});
}

In this class, we define different kinds of events by extending the abstract event class.
For example, when the user presses the Get Weather button, the WeatherRequest event is triggered.
Here I've also created a final field called cityName. It's nothing but a string inputted by the user in the search text field.
We have to pass it to the event in order to access it in our bloc.
Now let's implement weather_state.dart class

weather_state.dart :

/*import statements*/
part of 'weather_bloc.dart';

@immutable
abstract class WeatherState {}
class WeatherInitial extends WeatherState {}
class WeatherLoadInprogress extends WeatherState {}
class WeatherLoadSuccess extends WeatherState {
final Weather weather;
WeatherLoadSuccess({required this.weather});
}
class WeatherLoadFailure extends WeatherState {
final String error;
WeatherLoadFailure({required this.error});
}

In this class, we define different kinds of states (For example, LoadingInProgress state, LoadSuccess state, LoadFailure state).
For example, your app is fetching user data from an external API. Now when the user requests their data, initially we passLoadingInProgress which represents that the data is currently loading and we can show ProgressIndicator in UI. After data is received we change the state and pass the LoadSuccess state with the requested data. And if for some reason, something went wrong or some error occurred then we will pass LoadFailure for showing the user that the app has failed to fetch data.
In our case, we have 4 states -
WeatherInitial - For initial stage
WeatherLoadInprogress - For telling the app that weather data is in progress,
WeatherLoadSuccess - After weather data has been received we change our UI state and show the temperature data of the specified city.
WeatherLoadFailure - For Error handling .
Now that we've implemented all the Events and States. We can now go to weather_bloc.dart and can start implement mapEventToStatemethod.

Back to `weather_bloc.dart`:

So now that we have Events, we can now handle those events and perform our operation.

class WeatherBloc extends Bloc<WeatherEvent, WeatherState> {
final _weatherRepository = WeatherRepository();
WeatherBloc() : super(WeatherInitial());

@override
Stream<WeatherState> mapEventToState(WeatherEvent event) async* {
  if (event is WeatherRequest) {
    yield WeatherLoadInprogress();

    try {
      final weatherResponse =
          await _weatherRepository.getWeather(event.cityName);
      yield WeatherLoadSuccess(weather: weatherResponse);
    } catch (e) {
      yield WeatherLoadFailure(error: e.toString());
    }
  }
}
}

Here we are handling different events with if-else if-else. You can use switch-case too.
In this, we check for different events and return the relevant states to the UI.
In our case, we are checking if the Event is WeatherRequest, then we have to first of all pass the WeatherLoadInProgress state that tells the app that data is currently fetching.
And after receiving the response from the Repository we can then pass the WeatherLoadSuccess state with the data, and update the UI state.
Now the final step is to provide this data to the UI. Let's do this.

Step 5: How to access `bloc` data in UI?.

Now that we have created the bloc and implemented all the functionalities we need to somehow provide this bloc to the widget tree so that we can use the weather data and display it on the screen. And also we have to bind the Get Weather button.
Before that, we have to understand different Widgets provided by bloc -
BlocProvider, BlocBuilder, BlocListener, BlocConsumer, RepositoryProvider.

BlocProvider

BlocProvider widget provides a bloc to its children (i.e Widgets).
BlocProvider is used as dependency injection (DI) widget so that a single instance of a bloc can be provided to multiple widgets within a subtree.
If you don't know about Dependency Injection, you can check this out -
https://dhruvnakum.xyz/master-the-art-of-dependency-injection
Okay. So now we know what BlocProvider does, where can we put it?
We have to put it at the place from where all the children can access the bloc. Can you guess that place?
Its non-other than our favorite MaterialApp 🎉🎉
So let's wrap the BlocProvider inside MaterialApp
Go to main.dart.

class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
  return BlocProvider(
    create: (context) => WeatherBloc(),
    child: MaterialApp(
      home: WeatherApp(),
    ),
  );
}
}

That's it. Now we can access our bloc via BlocProvider.of<WeatherBloc>(context).
BlocProvider has one lazy parameter. By default, it's true. It is used to lazily load the bloc. It means whenever anyone tries to use the bloc then it will be initialized.
To override this functionality we can change the value of lazy to false.
Now you might have asked a question, that what if we have multiple blocs. How can we provide all the bloc from the main.dart?
One way is to nest all the bloc one inside another -

BlocProvider(
  BlocProvider(
    BlocProvider(
        .....

😅 Don't be scared. There is an easy approach. Don't use this

MultiBlocProvider

Bloc provides us a MultiBlocProvider widget that takes a List of Bloc and provides it to its children. Let me demonstrate.

class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
  return MultiBlocProvider(
    providers: [
      BlocProvider(create: (context) => WeatherBloc(),),
      BlocProvider(create: (context) => NetworkBloc(),),
      BlocProvider(create: (context) => StorageBloc(),),
    ],
    child: MaterialApp(
      home: WeatherApp(),
    ),
  );
}
}

Isn't it cool? That's the power of MultiBlocProvider 🦾

BlocBuilder:

BlocBuilder is a widget that helps Re-building the UI based on State changes.
In our case we want our UI to update the state when the user presses the Get Weather button.
BlocBuilder builds the UI every single time state changes
So, it's very necessary to place BlocBuilder around the Widget that we want to rebuild.
You can also wrap the whole Widget inside the BlocBuilder (i.e around the Scaffold), but it's not a good way. Because think about the time and processing power that will be consumed when your whole widget tree rebuilds just to update a Text widget inside the tree. So make sure you wrap the BlocBuilder around the widget that needs to be rebuild when the state changes.
In our case, we have to update the whole page. Because when the user presses the GetWeather button we want to show a Circular Progress Indicator instead of what we have previously.
So let's add BlocBuilder inside the body

body: BlocBuilder<WeatherBloc, WeatherState>(
      builder: (context, state) {
        return ...
   }
)

BlocBuilder takes two things bloc, and state.
builder function is required which takes two parameters. context and the state which is of type WeatherState in our case. And it should return Widget in response.
We can explicitly provide the bloc in BlocBuilder by passing the bloc inside bloc property of BlocBuilder

BlocBuilder<WeatherBloc, WeatherState>(
bloc: blocA, // provide the local bloc instance
builder: (context, state) {
   return ...
}
)

If the bloc parameter is omitted, BlocBuilder will automatically perform a lookup using BlocProvider and the current BuildContext.
Only specify the bloc if you wish to provide a bloc that will be scoped to a single widget and isn't accessible via a parent BlocProvider and the current BuildContext.
buildWhen parameter takes the previous bloc state and current bloc state and returns a boolean. If buildWhen returns true, builder will be called with state and the widget will rebuild. If buildWhen returns false, builder will not be called with state and no rebuild will occur.

BlocBuilder<WeatherBloc, WeatherState>(
buildWhen: (previousState, state) {
},
builder: (context, state) {
  return ...
}
)

We can conditionally render our widget based on the state with the help of the state parameter. Let's conditionally render the widget of our weather app based on different states. And call the WeatherRequest event on the Get Weather button press.

BlocBuilder<WeatherBloc, WeatherState>(
      builder: (context, state) {
        if (state is WeatherLoadInprogress)
          return Center(
            child: CircularProgressIndicator(),
          );
        else if (state is WeatherLoadFailure)
          return Center(
            child: Text("Something went wrong"),
          );
        else if (state is WeatherLoadSuccess)
          return WeatherWidget()
        else
          return Container();
      },
    ),
  );
}
}

You can access your Bloc by - BlocProvider.of(context) or context.

context.read<WeatherBloc>().add(Event());
// or
BlocProvider.of<WeatherBloc>(context)add(Event())

BlocListener:

As the name suggests, this will listen to any state change as BlocBuilder does.
But instead of building the widget like BlocBuilder, it takes one function, listener, which is called only once per state, not including the initial state.
Example: Navigation, Showing a SnackBar, Showing a Dialog, etc...
It also has a bloc parameter. Only specify the bloc if you wish to provide a bloc that is otherwise not accessible via BlocProvider and the current BuildContext.
The listenWhen parameter is the same as BlocBuilder's buildWhen but for Listener.
The whole idea of BlocListener is - It is not responsible for building/updating the widget like BlocBuilder does.
It only listens to the state changes and performs some operation. The operation could be (Navigating to other screens when state changes, Showing Snackbar on a particular state, etc).
Let's say we want to show a snackbar on WeatherLoadInProgress state -

Wrap the body inside BlocListener

body: BlocListener<WeatherBloc, WeatherState>(
      listener: (context, state) {
        if (state is WeatherLoadInprogress) {
          ScaffoldMessenger.of(context).showSnackBar(
            SnackBar(
              content: Text("Loading"),
            ),
          );
        }
    },
child : BlocBuilder<WeatherBloc, WeatherState>(
    builder: // ...
  )
)

Output:

MultiBlocListener:

MultiBlocListener is a Flutter widget that merges multiple BlocListener widgets into one. MultiBlocListener improves the readability and eliminates the need to nest multiple BlocListeners
By using MultiBlocListener we can go from:

BlocListener<BlocA, BlocAState>(
listener: (context, state) {},
child: BlocListener<BlocB, BlocBState>(
  listener: (context, state) {},
  child: BlocListener<BlocC, BlocCState>(
    listener: (context, state) {},
    child: ChildA(),
  ),
),
)

MultiBlocListener(
listeners: [
  BlocListener<BlocA, BlocAState>(
    listener: (context, state) {},
  ),
  BlocListener<BlocB, BlocBState>(
    listener: (context, state) {},
  ),
  BlocListener<BlocC, BlocCState>(
    listener: (context, state) {},
  ),
],
child: ChildA(),
)

BlocConsumer:

As of now we are building a widget using BlocBuilder and showing the snackbar using BlocListener.
Is there any easy way to combine both in a single widget? Hell yeah 😎
Bloc provide BlocConsumer widget, which combines both BlocListener and BlocBuilder.
So instead of writing BlocListener and BlocBuilder separately we can do -

BlocConsumer<BlocA, BlocAState>(
listener: (context, state) {
 if (state is WeatherLoadInprogress) {
   ScaffoldMessenger.of(context).showSnackBar(
     SnackBar(
       content: Text("Loading"),
      ),
    );
   }
},
builder: (context, state) {
  // return widget 
}
)

An optional listenWhen and buildWhen can be implemented for more granular control over when listener and builder are called.

RepositoryProvider:

It is the same widget as BlocProvider.
But the main difference is BlocProvider provides a single instance of bloc to its children whereas RepositoryProvider provides repositories to its children.
It is used as a dependency injection (DI) widget so that a single instance of a repository can be provided to multiple widgets within a subtree.
If you want to know more about dependency injection -
https://dhruvnakum.xyz/master-the-art-of-dependency-injection
Example:

RepositoryProvider(
create: (context) => WeatherRepository(),
child: ChildWidget(),
);

Widget can access this repository by -

context.read<WeatherRepository>();
// or
RepositoryProvider.of<WeatherRepository>(context)

MultiRepositoryProvider:

As the name suggests, it provides multiple repositories.
Example:

MultiRepositoryProvider(
providers: [
  RepositoryProvider<RepositoryA>(
    create: (context) => RepositoryA(),
  ),
  RepositoryProvider<RepositoryB>(
    create: (context) => RepositoryB(),
  ),
  RepositoryProvider<RepositoryC>(
    create: (context) => RepositoryC(),
  ),
],
child: ChildA(),
)

Step 6: Final Step

Now by using the above knowledge of BlocBuilder, BlocProvider, BlocListener, etc we can now complete our weather app.
So Let's first provide our bloc :
main.dart

class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
  return BlocProvider(
    create: (context) =>
        WeatherBloc()..add(WeatherRequest(cityName: "Ahmedabad")),
    child: MaterialApp(
      home: WeatherApp(),
    ),
  );
}
}

Here I've added an Event WeatherRequest when calling WeatherBloc, because we want the initial city to show. here I've provided a static city name. You can take the user's current location and provide it here to show the initial location of the user.
Wrap body inside BlocConsumer and add WeatherRequest Event on button click to fetch new city weather:
weather_app.dart

class WeatherApp extends StatelessWidget {
final _cityController = TextEditingController();
@override
Widget build(BuildContext context) {
  return Scaffold(
    resizeToAvoidBottomInset: false,
    appBar: AppBar(
      title: Text("Weather App"),
      centerTitle: true,
    ),
    body: BlocConsumer<WeatherBloc, WeatherState>(
      listener: (context, state) {
        if (state is WeatherLoadInprogress) {
          ScaffoldMessenger.of(context).showSnackBar(
            SnackBar(
              content: Text("Loading"),
            ),
          );
        }
      },
      builder: (context, state) {
        if (state is WeatherLoadInprogress)
          return Center(
            child: CircularProgressIndicator(),
          );
        else if (state is WeatherLoadFailure)
          return Center(
            child: Text("Something went wrong"),
          );
        else if (state is WeatherLoadSuccess)
          return Padding(
            padding: EdgeInsets.symmetric(horizontal: 12.0),
            child: Column(
              mainAxisAlignment: MainAxisAlignment.spaceAround,
              children: [
                TextFormField(
                  controller: _cityController,
                  decoration: InputDecoration(
                    hintText: "Enter city name",
                    border: OutlineInputBorder(),
                  ),
                ),
                Column(
                  children: [
                    Image.asset(
                      "assets/images/sun.png",
                      height: 200,
                      width: 200,
                    ),
                    SizedBox(
                      height: 20,
                    ),
                    Text(
                      state.weather.name,
                      style: Theme.of(context).textTheme.headline3,
                    ),
                    SizedBox(
                      height: 5,
                    ),
                    Text(
                      state.weather.main["temp"].toString(),
                      style: Theme.of(context).textTheme.headline4!.copyWith(
                          fontWeight: FontWeight.bold, color: Colors.black),
                    ),
                  ],
                ),
                ElevatedButton(
                  onPressed: () {
                    if (_cityController.text.isNotEmpty) {
                      context.read<WeatherBloc>().add(
                            WeatherRequest(
                              cityName: _cityController.text,
                            ),
                          );
                    }
                  },
                  child: Text("Get Weather"),
                )
              ],
            ),
          );
        else
          return Container();
      },
    ),
  );
}
}

Final Output:

Folder Structure For Bloc:

In business_logic folder you can provide all your bloc.
In data folder we have data_provider where you provide different providers, model where you define your data model, and repositories folder where you define all the repositories.
In presentation folder you can have screen folder, pages, widgets folder where you implement UI.

Final Project Repo:

https://github.com/red-star25/bloc_blog

Wrapping Up

Bloc pattern is quite hard to understand as it involves advance many concepts. But as soon as you start using it and playing around with it, you'll definitely master it. Trust me.
When I started learning Bloc, trust me it took a lot of time to understand all the concepts. But as soon as I started using it by making small applications it felt easy.
So, my advice is to start applying the concepts you have learned in this article by making small applications.
Hope this article helped to clear your doubts and concepts about Bloc. If It did then make sure you share it with others.
And also don't forget to share your feedback in the comment.
Thanks for reading 😀. See you in the next article
Until then...

Flutter Bloc : A Complete Guide

What is Bloc and its Architecture? What is BlocBuilder, BlocProvider, BlocListener, BlocConsumer, RepositoryProvider? Folder Structure For Bloc.

Intro

What is Bloc?

🖼️ UI (Presentation Layer) :

🦾Bloc (Business Logic Layer):

⚙️Data Layer :

Event

State

Implementing Bloc:

Step 1: Create a Flutter Application

Step 2: Project Setup

Final UI

Step 3: Install packages

Step 4: Create `bloc` files

`weather_bloc.dart` :

`weather_event.dart` :

`weather_state.dart` :

Back to `weather_bloc.dart`:

Step 5: How to access `bloc` data in UI?.

BlocProvider

MultiBlocProvider

BlocBuilder:

BlocListener:

MultiBlocListener:

BlocConsumer:

RepositoryProvider:

MultiRepositoryProvider:

Step 6: Final Step

Folder Structure For Bloc:

Final Project Repo:

Wrapping Up

Flutter Bloc : A Complete Guide

What is Bloc and its Architecture? What is BlocBuilder, BlocProvider, BlocListener, BlocConsumer, RepositoryProvider? Folder Structure For Bloc.

Intro

What is Bloc?

🖼️ UI (Presentation Layer) :

🦾Bloc (Business Logic Layer):

⚙️Data Layer :

Event

State

Implementing Bloc:

Step 1: Create a Flutter Application

Step 2: Project Setup

Final UI

Step 3: Install packages

Step 4: Create bloc files

weather_bloc.dart :

weather_event.dart :

weather_state.dart :

Back to weather_bloc.dart:

Step 5: How to access bloc data in UI?.

BlocProvider

MultiBlocProvider

BlocBuilder:

BlocListener:

MultiBlocListener:

BlocConsumer:

RepositoryProvider:

MultiRepositoryProvider:

Step 6: Final Step

Folder Structure For Bloc:

Final Project Repo:

Wrapping Up

Did you find this article valuable?

Step 4: Create `bloc` files

`weather_bloc.dart` :

`weather_event.dart` :

`weather_state.dart` :

Back to `weather_bloc.dart`:

Step 5: How to access `bloc` data in UI?.