Скачать или смотреть How to Pass Future int to Super Class in Flutter BLoC Pattern

Learn how to properly pass a `Future int ` to your superclass in Flutter's BLoC pattern to retain state between app restarts.
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This video is based on the question https://stackoverflow.com/q/63360764/ asked by the user 'mig001' ( https://stackoverflow.com/u/12616968/ ) and on the answer https://stackoverflow.com/a/63366480/ provided by the user 'DNS' ( https://stackoverflow.com/u/3177054/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Understanding the Problem: Retaining State in a Flutter Counter App

When developing a Flutter application, especially one that employs the BLoC (Business Logic Component) pattern, you may encounter issues with state management. For instance, if you've created a simple counter app, you may find that every time you restart the application, the counter resets to zero. This can be frustrating, particularly if you want to keep the last counted value when the app is closed.

In the given scenario, you have successfully stored the current counter value using SharedPreferences. However, while trying to load the saved value to initialize the CounterInitialState, you're faced with a type mismatch error. The error states that a Future<int> cannot be assigned to a parameter expecting an int. Let’s break down how to solve this problem effectively.

Solution: Using FutureBuilder

To handle this situation, you can utilize the FutureBuilder widget in Flutter. This widget is designed to work with asynchronous operations, allowing you to build your UI depending on whether your Future is complete or still loading.

Step-by-Step Implementation

Step 1: Modify Your CounterBloc

First, ensure your CounterBloc class has the necessary method to retrieve the saved counter value. You've already done this with loadData(), which returns a Future<int>.

Step 2: Integrate FutureBuilder in Your Widget

Next, wrap your widget where you want to display the counter with a FutureBuilder. This will enable your app to build the UI based on the future value being loaded.

Here's an example of how to implement it:

[[See Video to Reveal this Text or Code Snippet]]

Step 3: Use the Loaded Value in Your App

Finally, you can now utilize the retrieved value from FutureBuilder to set your initial state in the BLoC. This ensures that when your application starts, it will reflect the last saved count instead of resetting to zero.

Important Points to Note

Async Handling: Ensure that you handle the asynchronous nature of fetching data properly, using ConnectionState to show loading states.

Error Handling: Implement error handling within the FutureBuilder to manage any issues while retrieving the counter value.

State Management: Remember that state management is crucial in Flutter apps. Using FutureBuilder facilitates a reactive way of handling state based on asynchronous operations.

Conclusion

By applying the FutureBuilder widget, you can easily resolve the issue of passing Future<int> to your superclass in your Flutter BLoC implementation. This method not only resolves type mismatches but also allows for a seamless user experience, where your counter app maintains state even after being closed and reopened.

Now go ahead and implement this solution in your Flutter project, and enjoy a more robust counter app!