How to Cancel Old Function Calls in Cubit for Flutter Projects

Discover how to effectively manage function calls in your Flutter app using Cubit. Cancel previous calls and ensure smooth performance with the right strategy.
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How to Cancel Old Function Calls in Cubit for Flutter Projects

When developing applications with Flutter, handling asynchronous operations can sometimes be a challenge. One common problem developers encounter is the need to cancel old function calls when a new event occurs. In this guide, we will explore a specific scenario involving Cubit, a state management solution for Flutter, and provide you with an effective solution to tackle this issue.

The Problem

Imagine you're using Cubit in your Flutter project. You have a function, whenDisconnectedFunction, that performs a long-running operation (in this case, it simulates a delay using Future.delayed). During this operation, if a new event occurs (for instance, the user connects to the internet), you want to call another function, whenConnectedFunction. However, you run into a problem: the previous function continues to execute even after starting the new one.

Illustrative Example

In your current setup, the following happens:

You call whenDisconnectedFunction, which outputs test2 and starts a 10-second delay.

If whenConnectedFunction is called before the delay ends, it prints test1, yet test3 from whenDisconnectedFunction still executes, leading to unintended behavior.

This situation can confuse users and degrade the app's performance. So, how can we prevent previous function calls from completing when new events arise?

The Solution

Fortunately, there is a straightforward way to manage this using the BLoC (Business Logic Component) pattern alongside the bloc_concurrency package. This allows you to control how events are processed in your Cubit and gives you the ability to restart or cancel them effectively.

Step-by-Step Guide

Add Dependency: First, ensure that you include the bloc_concurrency package in your pubspec.yaml file:

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Using restartable Events: By using restartable events, you can ensure that any previous execution is paused or canceled when a new event is triggered. Here's how you can implement it:

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Leveraging Concurrency: By incorporating the concurrency features of the bloc_concurrency, you can manage how the events are executed. For whenDisconnected function calls, simply mark the handling of this event as restartable.

Conclusion

By implementing the above approach using the bloc_concurrency package, you can successfully manage how your Cubit handles old function calls in your Flutter project. This helps in providing a smoother user experience and optimal app performance. Next time a user connects while your app is processing a long-running task, you can ensure that only the relevant operations execute.

By adopting better event management strategies, such as restartable events, you can handle similar challenges and create more responsive Flutter applications. Happy coding!