DI Code Generation with Annotations (CherryPick)

CherryPick enables smart, fully-automated dependency injection (DI) for Dart/Flutter via annotations and code generation. This eliminates boilerplate and guarantees correctness—just annotate, run the generator, and use!

1. How does it work?

You annotate classes, fields, and modules using [cherrypick_annotations].
The [cherrypick_generator] processes these, generating code that registers your dependencies and wires up fields or modules.

You then run:

dart run build_runner build --delete-conflicting-outputs

— and use the generated files in your app.

2. Supported Annotations

Annotation	Where	Purpose
`@injectable()`	class	Enables auto field injection; mixin will be generated
`@inject()`	field	Field will be injected automatically
`@scope()`	field/param	Use a named scope when resolving this dep
`@named()`	field/param	Bind/resolve a named interface implementation
`@module()`	class	Marks as a DI module (methods = providers)
`@provide`	method	Registers a type via this provider method
`@instance`	method	Registers a direct instance (like singleton/factory)
`@singleton`	method/class	The target is a singleton
`@params`	param	Accepts runtime/constructor params for providers

You can combine annotations as needed for advanced use-cases.

3. Practical Examples

A. Field Injection (recommended for widgets/classes)

import 'package:cherrypick_annotations/cherrypick_annotations.dart';

@injectable()
class MyWidget with _$MyWidget { // the generated mixin
  @inject()
  late final AuthService auth;

  @inject()
  @scope('profile')
  late final ProfileManager profile;

  @inject()
  @named('special')
  late final ApiClient specialApi;
}

After running build_runner, the mixin _$MyWidget is created.
Call MyWidget().injectFields(); (method name may be _inject or similar) to populate the fields!

B. Module Binding (recommended for global app services)

@module()
abstract class AppModule extends Module {
  @singleton
  AuthService provideAuth(Api api) => AuthService(api);

  @provide
  @named('logging')
  Future<Logger> provideLogger(@params Map<String, dynamic> args) async => ...
}

Providers can return async(Future<T>) or sync.
@singleton = one instance per scope.

4. Using the Generated Code

Add to your pubspec.yaml:

dependencies:
  cherrypick: any
  cherrypick_annotations: any

dev_dependencies:
  cherrypick_generator: any
  build_runner: any

Import generated files (e.g. app_module.module.cherrypick.g.dart, your_class.inject.cherrypick.g.dart).

final scope = openRootScope()
  ..installModules([$AppModule()]);

For classes with auto-injected fields, mix in the generated mixin and call the injector:
```
final widget = MyWidget();
widget.injectFields(); // or use the mixin's helper
```
All dependencies are now available and ready to use!

5. Advanced Features

Named and Scoped dependencies: use @named, @scope on fields/methods and in resolve().
Async support: Providers or injected fields can be Future (resolveAsync).
Runtime parameters: Decorate a parameter with @params, and use resolve<T>(params: ...).
Combining strategies: Mix field injection (@injectable) and module/provider (@module + methods) in one app.

6. Troubleshooting

Make sure all dependencies are annotated, imports are correct, and run build_runner on every code/DI change.
Errors in annotation usage (e.g. @singleton on non-class/method) will be shown at build time.
Use the .g.dart files directly—do not edit them by hand.

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