A portrait painting style image of a pirate holding an iPhone.

by The Captain

July 25, 2023

Title: Flutter MobX State Management: Simplify Reactive Programming

MobX is a popular state management library in Flutter that simplifies the implementation of reactive programming. It allows you to efficiently manage application state by automatically tracking and updating dependencies, which leads to cleaner and more maintainable code.

To use MobX in your Flutter project, you need to add the mobx and flutter_mobx packages to your pubspec.yaml file:

    sdk: flutter
  mobx: ^2.0.0
  flutter_mobx: ^2.0.0

Once the packages are added, you can start leveraging the power of MobX. Let's create a simple example to demonstrate how MobX works.

Step 1: Define Observables and Actions

Create a new file called counter_store.dart and define a simple counter store using MobX:

// counter_store.dart

import 'package:mobx/mobx.dart';

part 'counter_store.g.dart'; // This is required for code generation

class CounterStore = _CounterStore with _$CounterStore;

abstract class _CounterStore with Store {
  int counter = 0;

  void increment() {

  void decrement() {

In the above code, we create a class called CounterStore and annotate it with the @Store decorator from MobX. The counter variable is marked as an observable using the @observable decorator, and the increment() and decrement() methods are marked as actions using the @action decorator.

Step 2: Generate MobX Code

MobX utilizes code generation to create necessary boilerplate code. In order to generate the required code, run the following command in your project directory:

flutter packages pub run build_runner build

This command will generate a file named counter_store.g.dart containing the necessary code for MobX to work. Make sure to import this file wherever you use the CounterStore.

Step 3: Use MobX in the UI

Now, let's use MobX in a Flutter widget to demonstrate how reactive programming simplifies state management. Create a new file called counter_screen.dart and add the following code:

// counter_screen.dart

import 'package:flutter/material.dart';
import 'package:flutter_mobx/flutter_mobx.dart';
import 'counter_store.dart';

class CounterScreen extends StatelessWidget {
  final CounterStore counterStore = CounterStore();

  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('MobX Counter'),
      body: Center(
        child: Column(
          children: [
              builder: (_) {
                return Text(
                  'Count: ${counterStore.counter}',
                  style: TextStyle(fontSize: 24),
            SizedBox(height: 16),
              child: Text('Increment'),
              onPressed: () => counterStore.increment(),
              child: Text('Decrement'),
              onPressed: () => counterStore.decrement(),

In the above code, we create a CounterStore instance and use the Observer widget from flutter_mobx to observe changes in the counterStore.counter value. Whenever the counter changes, the text widget inside the Observer builder is automatically updated.

Finally, we wrap the Increment and Decrement buttons with RaisedButton widgets, which call the respective actions when pressed.


MobX is a powerful state management library for Flutter, simplifying reactive programming by automatically tracking and updating dependencies. With its observables and actions, you can easily manage and update application state. By using the Observer widget, UI components can efficiently react to state changes. MobX is a great choice for projects that require fine-grained reactivity and declarative state management.