providedIn
The providedIn property is used within the @Injectable decorator to specify where the service should be provided. This is a more modern and preferred way to provide services in Angular.
Global Scope: When you use providedIn: 'root', the service is registered with the root injector, making it a singleton and available throughout the entire application.
@Injectable({ providedIn: 'root', }) export class MyService { constructor() { } }
Feature Module Scope: You can also specify a feature module to limit the scope of the service.
@Injectable({ providedIn: SomeFeatureModule, }) export class MyService { constructor() { } }
providers Array
The providers array is used within the @NgModule or @Component decorators to register services. This method is more traditional and offers more granular control over the scope of the service.
Module Level: When you add a service to the providers array in an @NgModule, the service is available to all components declared in that module.
@NgModule({ providers: [MyService] }) export class AppModule { }
Component Level: When you add a service to the providers array in a component’s decorator, the service is available only to that component and its children.
@Component({ selector: 'app-my-component', providers: [MyService], template: `<p>{{ message }}</p>`, }) export class MyComponent { constructor(private myService: MyService) { } }
Key Differences
- Scope:
- providedIn: 'root': Service is available application-wide.
- providers array: Service scope can be limited to a specific module or component.
- Singleton:
- providedIn: 'root': Ensures a singleton instance across the entire application.
- providers array: Can create multiple instances if provided at different levels (e.g., module and component).
- Tree Shaking:
- providedIn: Supports tree shaking, meaning unused services can be removed during the build process.
- providers array: Does not support tree shaking as effectively.
Conclusion
Using providedIn is generally recommended for its simplicity and efficiency, especially for services that need to be available application-wide. The providers array is useful when you need more control over the scope and lifecycle of your services.
Happy coding!! 😊
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