Flutter BLoC Tutorial: Manage State with the BLoC Pattern

Using the BLoC Pattern to Manage State in Flutter

Flutter is an open-source mobile application development framework created by Google. It’s used to develop apps for both Android and iOS. Flutter makes it easy to build complex, reactive UI quickly and efficiently, but managing state in large applications can be a challenge. That's where the BLoC pattern comes in. In this tutorial, we’ll discuss how to use the BLoC pattern to manage state in Flutter apps easily and efficiently.

What is the BLoC Pattern?

The BLoC pattern stands for Business Logic Component. It's an architectural pattern that uses patterns from functional programming and reactive programming to simplify the communication between UI elements and business logic. It was designed by Google and is heavily based on their Principles of reactive programming. Basically, the BLoC pattern uses streams to manipulate data between different parts of the app, instead of using state variables. This makes it easier to scale apps and maintain them over time.

How Does it Work in Flutter?

In Flutter, the BLoC pattern works by creating a “business logic component”, which is basically a class with methods that mediate communication between the UI elements and the app’s business logic. This component is then responsible for maintaining the app’s state, and publishes updates to any other part of the app that needs to know about it. Other parts of the app such as widgets, can then listen to the BLoC’s events via streams to react to state changes.

Example App

Let’s look at a basic example of how the BLoC pattern can be used in a Flutter app to manage state. We’ll use a simple counter app that counts up when a button is pressed. First, we’ll start by creating a State Provider class that will manage our app’s state. This class will have a single instance that will be accessible throughout the app. Then, we’ll create a BLoC class that will contain methods for incrementing and decrementing the counter variable.

Next, we’ll create a widget that will display the counter value and a button to trigger incrementing or decrementing the counter. In the widget’s build method, we’ll listen to the BLoC’s stream and update the display accordingly. Finally, we’ll hook up the button to the BLoC’s methods that increment/decrement the counter.

Conclusion

The BLoC pattern is an excellent way to manage state in large Flutter apps. It makes it easier to separate business logic from UI, and makes it easier to scale apps without much effort. With a few simple steps, you can get started using the BLoC pattern in your Flutter apps today!