ng_di 1.0.0

Dependency injection package taken from angular DI.

A Dependency Injection package taken from angular DI.

Usage

Create one of the examples shown below

Inject by Type

Create an Injector by using annotation @GenerateInjector and pass the List of types, then the generator will create the respective injector.

@GenerateInjector([Engine, Car])
final injector = injector$Injector();

Full code:

library example.type;

import 'package:ng_di/ng_di.dart';

part 'type.ng_di.g.dart';

@Injectable()
class Engine {
  String name;

  Engine();
}

@Injectable()
class Car {
  final Engine engine;

  Car(this.engine);
}

//tag::injector[]
@GenerateInjector([Engine, Car])
final injector = injector$Injector();
//end::injector[]

main() {
  assert(injector.get(Car).engine.name == null);

  injector.get(Car).engine.name = 'my-engine';
  assert(injector.get(Car).engine.name == 'my-engine');

  print('Carg.engine.name: ${injector.get(Car).engine.name}');
}

Inject using @Inject() annotation

In this case you can specify the token corresponding to the dependency that will be injected. For example:

library example.inject;

import 'package:ng_di/ng_di.dart';

part 'inject.ng_di.g.dart';

const v4_engine_token = OpaqueToken<String>('v4_engine_token');
const v8_engine_token = OpaqueToken<String>('v8_engine_token');
const truck_token = OpaqueToken<String>('truck_token');

class Engine {
  String name;

  Engine([@Inject(v4_engine_token) this.name]);
}

class Car {
  final Engine engine;

  Car(this.engine);
}

_truckFactory(String name) => Car(Engine(name));

@GenerateInjector([
  Provider(v4_engine_token, useValue: 'v4-engine'),
  Provider(v8_engine_token, useValue: 'v8-engine'),
  Engine,
  Car,
  Provider(truck_token, useFactory: _truckFactory, deps: [v8_engine_token])
])
final injector = injector$Injector();

main() {
  print('Car.engine: ${injector.get(Car).engine.name}');
  assert(injector.get(Car).engine.name == 'v4-engine');
  print('truck.engine: ${injector.get(truck_token).engine.name}');
  assert(injector.get(truck_token).engine.name == 'v8-engine');
}

Inject using @Optional() annotation

In this case we can mark dependencies as optional, so if the value is not injected then a null value is passed. For example:

library example.optional;

import 'package:ng_di/ng_di.dart';

part 'optional.ng_di.g.dart';

@Injectable()
class Engine {
}

@Injectable()
class Car {
  final Engine engine;

  Car(@Optional() this.engine);
}

class Truck {
  final Engine engine;

  Truck([this.engine]);
}

class Boat {
  final Engine engine;

  Boat({this.engine});
}

@GenerateInjector([Car, Truck, Boat])
final injector = injector$Injector();

main() {
  print('Carg.engine: ${injector.get(Car).engine}');
  print('Truck.engine: ${injector.get(Truck).engine}');
  print('Boat.engine: ${injector.get(Boat).engine}');
}

Inject using @Self() annotation

In this case we can mark dependencies as self, so the injector should retrieve a dependency only from itself. For example:

library example.self;

import 'package:ng_di/ng_di.dart';

part 'self.ng_di.g.dart';

@Injectable()
class Engine {
  String name;

  Engine();
}

@Injectable()
class Car {
  final Engine engine;

  Car(@Self() this.engine);
}

@GenerateInjector([Engine, Car])
final injector = injector$Injector();

@GenerateInjector([Engine])
final parentInjector = parentInjector$Injector();

@GenerateInjector([Car])
final childInjector = childInjector$Injector(parentInjector);

main() {
  assert(injector.get(Car).engine.name == null);
  print('Car.engine: ${injector.get(Car).engine.name}');

  try {
    print('Car.engine: ${childInjector.get(Car).engine.name == null}');
  } catch (e) {
    print('error: $e');
  }
}

Inject using @SkipSelf() annotation

In this case we can mark dependencies as optional, so the dependency resolution should start from the parent injector. For example:

library example.skip_self;

import 'package:ng_di/ng_di.dart';

part 'skip_self.ng_di.g.dart';

@Injectable()
class Engine {
  String name;

  Engine();
}

@Injectable()
class Car {
  final Engine engine;

  Car(@SkipSelf() this.engine);
}

@GenerateInjector([Engine, Car])
final injector = injector$Injector();

@GenerateInjector([Engine])
final parentInjector = parentInjector$Injector();

@GenerateInjector([Car])
final childInjector = childInjector$Injector(parentInjector);

main() {
  try {
    print('Car.engine: ${injector.get(Car).engine.name == null}');
  } catch (e) {
    print('error: $e');
  }

  assert(childInjector.get(Car).engine.name == null);
  print('Car.engine: ${childInjector.get(Car).engine.name}');
}