widject_container 1.0.2

Dependency Injection Container to structure your application in loosely coupled components. Inspired by VContainer.

WidjectContainer

Dependency Injection package for Flutter

Simple DI package to help structure your Flutter application in loosely coupled components. Inspired by VContainer.

Features

• Explicit constructor injection within scopes.
  • No use of reflection/mirrors.
• Nested scope support to isolate dependencies by widget type.
• Async initialization of scoped dependencies.

Installation

Add the package with the command: flutter pub add widject_container or adding widject_container to your project's pubspec.yaml dependencies.

Basic Usage

Create a scope connected to a widget and register the required types. The type references are automatically resolved when requested within the scope.

class AppScope extends Scope<AppWidget> {
  AppScope(): super(null);

  @override
  void configure(ContainerRegister register) {
    register.add((r) => HelloWorldProvider(), Lifetime.transient).as<MessageProvider>();
    register.addWidget((r, key, _) => AppWidget(r.get(), key: key));
  }
}

Where classes are:

abstract class MessageProvider {
  String getMessage();
}

class HelloWorldProvider implements MessageProvider {
  @override
  String getMessage()
    => "Hello world!";
}

class AppWidget extends StatelessWidget {
  final MessageProvider _messageProvider;
  
  const AppWidget(this._messageProvider, {super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'WidjectContainer Demo',
      home: Scaffold(
        body: Text(_messageProvider.getMessage())
      )
    );
  }
}

Example of scope usage in main function is:

void main() {
  var app = AppScope().getWidget();
  runApp(app);
}

Widget Provider

Use WidgetProvider to instantiate widget types that have been registered within a scope. Dependencies are resolved and explicitly injected, as defined in the scope registration.

Example of registration:

class AppScope extends Scope<AppWidget> {
  ...

  @override
  void configure(ContainerRegister register) {
    ...
    register.addWidget((r, key, _) => NewWidget(r.get(), args, key: key));
  }
}

Example of usage through WidgetProvider:

class AppWidget extends StatelessWidget {
  final MessageProvider _messageProvider;
  final WidgetProvider _widgetProvider;
  
  const AppWidget(this._messageProvider, this._widgetProvider, {super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'WidjectContainer Demo',
      home: Scaffold(
        body: _widgetProvider.getWidget<NewWidget>())
      )
    );
  }
}

Nested Scopes

Connect the instantiation of a widget to a new scope, registering types and inheriting references from ancestor scopes. This can be useful when creating a new screen that requires a whole new set of dependencies.

class ScreenScope extends Scope<ScreenWidget>{
  ScreenScope(super.parentContainer);

  @override
  void configure(ContainerRegister register) {
    register.addWidget((r, key, args) => ScreenWidget(...));
  }
}

Where the scoped widget binding in the parent scope is:

class AppScope extends Scope<AppWidget> {
  ...

  @override
  void configure(ContainerRegister register) {
    ...
    register.addScopedWidget((r, key, _) => ScreenScope(r));
  }
}

Example of usage through WidgetProvider:

class AppWidget extends StatelessWidget {
  final MessageProvider _messageProvider;
  final WidgetProvider _widgetProvider;

  const AppWidget(this._messageProvider, this._widgetProvider, {super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'WidjectContainer Demo',
      home: Scaffold(
        body: TextButton(
          onPressed: () => _openChildWidget(context),
          child: Text(_messageProvider.getMessage()))));
  }

  _openChildWidget(BuildContext context) {
    Navigator.push(
      context,
      MaterialPageRoute(
        builder: (context) => _widgetProvider.getWidget<ScreenWidget>()));
  }
}

Credits

WidjectContainer is inspired by:

• VContainer.

Author

Claudio Mazza

License

MIT