bon_notifiers

bon_notifiers is a collection of custom notifiers and mixins that I use in my projects. This package provides various utilities to extend on flutters Notifier principle. Primarily focussing on handling asynchronous operations with less boilerplate.

For a full statemanagement solution you can bundle this package with provider and flutters default notifiers.

Features

  • AsyncNotifier<T>: A notifier taylored for handling asynchronous data.
  • AsyncListenableBuilder<T>: A widget that listens to AsyncListenable and rebuilds based on the state changes.
  • mixins: Reusable functionality for handling different states like loading, error, and result in your custom notifiers.

Example usage

Async Notifier

Using asyncnotifier as an object

final notifier = AsyncNotifier<String>();

// Set initial value
notifier.set('Initial data');

// Update value
notifier.update((result) => result + ' updated');

// Set error
notifier.setError('Something went wrong');

// Check flags
if (notifier.isLoading) {
  // Show loading indicator
} else if (notifier.hasError) {
  // From this point it is safe to acces error
  print(notifier.error!);
} else if (notifier.hasResult) {
  // From this point it is safe to acces result
  print(notifier.result!);
}

Extending async notifier

//For more complex usecases extending AsyncNotifier can be useful
class ComplexAsyncNotifier extends AsyncNotifier<Data> {
  ComplexAsyncNotifier({required this.repo}) {
    _init();
  }

  final ExampleRepository repo;
  
  //add more complex behaviours
  Future<void> _init(){
    try{
        final result = await repo.getData();
        set(result);
    }
    catch(e){
        setError(e);
    }
  }
  //add custom methods
  void swap(Data newData) {
    set(newData);
  }
}

final complexNotifier = ComplexAsyncNotifier();

// Using extended functionality
complexNotifier.swap();

AsyncListenableBuilder

AsyncListenableBuilder<String>(
  //pass the asyncNotifier (or a custom async listenable)
  asyncListenable: notifier,
  //the resultBuilder is executed when the asyncListenable optains a (new) result
  resultBuilder: (context, result, child) => Text(result),
  //the errorBuilder is executed when the asyncListenable optains an error
  errorBuilder: (context, error, child) => Text('Error: $error'),
  //a loadingIndicator can be optionally passed, this defaults to CircularProgressIndicator.adaptive
  loadingIndicator: CircularProgressIndicator(),
  //Like the native flutter ListenableBuilders, a static child can be provided if a part of the widget tree is not dependant on the notifier
  child: Text('This is a static widget'),
)

Error Mixin

The error mixin can be used as follows:

class MyErrorNotifier extends ChangeNotifier with ErrorNotifier {
  // A method to simulate fetching data and setting an error
  void fetchData() {
    try {
      throw Exception("Data fetch failed");
    } catch (error) {
      setError(error);  // Sets error using ErrorNotifier
    }
  }
}

final notifier = MyErrorNotifier();

//The mixin exposes hasError and error getters
if(notifier.hasError){
    print(notifier.error);
}

Loading mixin

The loading mixin can be used as follows:

class MyLoadingNotifier extends ChangeNotifier with LoadingNotifier {
  // A method to simulate data loading process
  void fetchData() {
    setLoading();  // Starts the loading state using LoadingNotifier

    // Simulating data fetch
    Future.delayed(Duration(seconds: 2), () {
      setNotLoading();  // Ends the loading state once data is fetched
      notifyListeners();
    });
  }
}

final notifier = MyErrorNotifier();

//The mixin exposes a loading boolean flag
print(notifier.isLoading);

Everything public class and method in this package is documented, so for more documentation you can go to the sourcecode

License

This project is licensed under the MIT License - see the LICENSE file for details.

Libraries

bon_notifiers