veto 0.0.3+2

A lightweight MVVM state management solution inspired by the FilledStacks stacked package.

📚 Veto

A lightweight MVVM state management solution originally inspired by the FilledStacks stacked package.

[veto_example_project.png]

Features

• Easy management of view models' lifecycle
• Automatic handling of initialization and disposal
• Support for view model states like initialising, initialised, busy, and error
• Reactive rebuilding of the widget tree when the view model's state changes
• Access to the build context within view models

Getting started

To use this package, add veto as a dependency in your pubspec.yaml file.

Importing

Import the package into your file:

import 'package:veto/veto.dart';

Usage

ViewModelBuilder

The ViewModelBuilder widget is the core class responsible for providing a view model to the widget tree and managing its lifecycle.

Use the ViewModelBuilder like this:

ViewModelBuilder<MyViewModel>(
  viewModelBuilder: () => MyViewModel(),
  builder: (context, model) {
    return Scaffold(
      appBar: AppBar(title: Text('Veto Example')),
      body: model.isBusy
          ? CircularProgressIndicator()
          : Text('Hello World!'),
    );
  },
)

Here, MyViewModel extends BaseViewModel.

BaseViewModel

Create your custom view model by extending the BaseViewModel class:

class MyViewModel extends BaseViewModel {
  int _counter = 0;

  int get counter => _counter;

  void incrementCounter() {
    setBusy(true);
    wait(1000).then((_) {
      _counter++;
      setBusy(false);
      rebuild();
    });
  }
}

In your view model, you can:

• Define properties and methods
• Access the context property (e.g., for navigation)
• Call rebuild to rebuild the widget tree
• Use setBusy and setError to manage the view model state

ViewModelState

ViewModelState is an enumeration that defines the different states a BaseViewModel can be in:

• isInitialising: The view model is currently initializing
• isInitialised: The view model has finished initializing
• isBusy: The view model is currently busy (e.g., fetching data)
• hasError: The view model has encountered an error

You can use the ViewModelState enum to display different UI based on the view model's state:

@override
Widget build(BuildContext context) {
  return ViewModelBuilder<MyViewModel>(
    viewModelBuilder: () => MyViewModel(),
    builder: (context, model) {
      Widget? content;
      switch (model.state) {
        case ViewModelState.isInitialising:
          content = CircularProgressIndicator();
          break;
        case ViewModelState.isInitialised:
          content = Text('Hello World!');
          break;
        case ViewModelState.isBusy:
          content = CircularProgressIndicator();
          break;
        case ViewModelState.hasError:
          content = Text('An error occurred');
          break;
      }
      return Scaffold(
        appBar: AppBar(title: Text('Veto Example')),
        body: content,
      );
    },
  );
}

Examples

Please see the example folder for a complete example of using Veto in a Flutter application.

Contributing

Contributions are welcome! If you find a bug or have a feature request, please open an issue.

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The entire package has extensive documentation. Reading the BaseViewModel class from top to bottom will give you a good idea of the benefits of this package. Also, a good example project, proper unit tests and some widget tests have been added pto illustrate and test the most important features of this package. If you have any questions feel free to contact me through codaveto.com.