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Preventing side effect functions in Flutter


Throughout my programming journey, I've learned that writing clean, efficient, and maintainable code is crucial. When working with Flutter, it's essential to avoid side effect functions that can cause unexpected issues and make the code harder to understand. Join me as we dive into the importance of steering clear of side effects and learn how to create well-crafted and reliable Flutter applications.

When composing a function, you're aware of its inputs, which are the parameters, and its output, which is the return value. Anything that goes beyond this and influences the world outside the function is considered a side effect.

void hello() {
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Printing something to the console constitutes a side effect since it impacts the world beyond the function. If you want to modify your function to eliminate side effects, you could rewrite it like this:

String hello() {
     return 'Hello!';
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Now, there's nothing within the function body that impacts the external environment. You'll need to print the string to the console outside of the function.

Grasping Side Effects

Side effects encompass any alterations happening outside the direct scope of a function or widget. Such changes can involve modifying state, executing network requests, carrying out I/O operations, accessing databases, or interacting with external services. Side effects can result in reduced predictability and make understanding your application's behavior challenging. Consequently, it's vital to use techniques that minimize side effects and ensure your app remains dependable and easy to maintain.

While it's acceptable and sometimes necessary for certain functions to have side effects, functions without side effects are generally easier to handle and comprehend. You can trust them to perform exactly as anticipated since they consistently return the same output for a given input. Functions of this type are also referred to as pure functions.

Adopt Reactive Programming:

Reactive programming is an approach that emphasizes handling state changes in a clear and foreseeable way. In Flutter, multiple reactive programming libraries exist, including Provider, Riverpod, Bloc, and MobX. These libraries let you segregate business logic from the user interface, facilitating improved control over side effects. By confining side effects to particular components, you can make certain that alterations remain contained and predictable.

Opt for the Suitable State Management Method:

Picking the right state management strategy can substantially decrease the incidence of side effects. Flutter provides a range of state management libraries, each possessing unique benefits and strong points. Libraries such as Provider and Riverpod promote the utilization of unchangeable data structures and impose one-way data flow. By following these principles, you can avoid unexpected side effects and boost the predictability of your application.

Leverage Async/Await and Futures:

Asynchronous tasks are frequently found in Flutter applications, particularly when working with network requests, file operations, or animations. Dart, the programming language employed in Flutter, offers robust asynchronous programming capabilities, such as async/await and Futures. By using these mechanisms, you can manage asynchronous operations more effectively and prevent possible side effects. The async/await syntax makes writing asynchronous code easier by enabling you to compose asynchronous tasks in a more synchronous manner, enhancing code readability and maintainability.

Restrict the Usage of Global Variables:

Global variables can lead to side effects as they can be accessed and altered from any part of your application. It's recommended to limit their use and instead confine related data and functions within particular components. By narrowing the scope of variables, you decrease the likelihood of unwanted side effects and render your code more modular and testable.

Conduct Rigorous Testing:

Testing is an essential part of any software development process, including Flutter. In-depth unit and integration testing can aid in identifying and preventing side effects in your application. Creating tests that encompass various situations and edge cases allows you to confirm the behavior of different components and ensure that side effects are managed properly. Automated tests serve as a safety measure, helping you detect regressions when making modifications and giving you confidence in your codebase's stability.

Steering clear of side effects is vital for developing dependable and maintainable Flutter applications. By embracing a reactive programming style, using suitable state management libraries, taking advantage of async/await and Futures, minimizing global variables, carrying out extensive testing, applying design patterns and architectural principles, and using Flutter's built-in widgets and APIs, you can significantly decrease the presence of side effects in your codebase. Prioritizing the avoidance of side effects paves the way for more predictable, high-performing, and error-free Flutter applications, ensuring a pleasant user experience and long-lasting success.


In conclusion, avoiding side effects is essential for building reliable and maintainable Flutter applications. By incorporating best practices and techniques, you can significantly reduce the occurrence of side effects in your codebase and create more predictable and performant applications. Embrace reactive programming and choose the right state management libraries, such as Provider or Riverpod, to ensure a clean separation of concerns. Leverage Dart's powerful async/await and Futures constructs to handle asynchronous operations efficiently. Limit the usage of global variables, localizing the scope of variables to make your code more modular and testable.

Furthermore, prioritize thorough testing, including unit and integration tests, to identify and prevent side effects, ensuring that your components behave as expected. By following these strategies and harnessing Flutter's built-in widgets and APIs, you'll create delightful user experiences and set your application up for long-term success. By consistently focusing on preventing side effects, you'll produce higher-quality, more stable, and easily maintainable codebases, ultimately leading to a positive impact on both the development process and user satisfaction.

Top comments (1)

christiankyony profile image
Christian Kyony

Hello, Thanks for this article. However, I'd love to see the generic advices to be complemented by more specific examples.