bon_notifiers 1.1.0

A collection of custom notifiers and notifier mixins

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<int>();

// Set loading
notifier.setLoading();

// Set value
notifier.set(0);

// Set error
notifier.setError(error);

// Null safe update value
notifier.update((value) => value+1)


// 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(error, message: 'Failed to fetch data');
    }
  }
  //add custom methods
  void editName(String newName) {
    update(
      (value) => repo.update(
          value.copyWith(name: newName),
          errorMessage: 'Failed to edit name'
        )
    );

  }
}

final complexNotifier = ComplexAsyncNotifier();

// Using extended functionality
complexNotifier.editName('Alice');

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, message: 'Failed to fetch data');
    }
  }
}

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
    });
  }
}

final notifier = MyErrorNotifier();

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

Listening for errors:

The AsyncListenable class exposes a listener that can be added to handle or log errors from one place.

AsyncListenable.errorListener =  (message, notifier, error, stackTrace){
  //log errors from one place so we dont have to put logger calls in every notifier
 logger.e(
    '$message in ${notifier.runtimeType}', 
    error: error, 
    stackTrace:  stackTrace
 );
}

This method will be called any time setError or update is called with a value in the message parameter.

Every public class and method in this package is documented, for more documentation see the api reference

License

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