Angular's dependency injection (DI) system is a powerful feature that provides the management of application-wide services. Among these, providedIn stands out as a concise and efficient way to specify where and how services should be injected within an Angular application. In this article, we'll see more about providedIn and explore its usage scenarios.
Prerequisites
What is Providedln strings ?
In Angular, the providedIn property is used within the @Injectable() decorator to specify the module or injector where the service should be provided. When you provide a service using providedIn, Angular automatically creates a provider for the service and registers it with the specified module or injector. This approach eliminates the need to manually add the service to the providers array of a module.
How providedIn Works ?
Consider a typical scenario where you have a service in your Angular application. Here's how you would typically provide it:
@Injectable({
providedIn: 'root'
})
export class MyService {
// Service logic here
}
In this example, providedIn: 'root' indicates that Angular should provide this service at the root level of the application. This means that the service is available throughout the entire application. Angular will instantiate the service once and share the same instance across all the components that inject it.
Alternatively, you can provide the service in a specific module. For example:
@Injectable({
providedIn: SomeModule
})
export class MyService {
// Service logic here
}
The module where you wish to offer the service is indicated by the term "SomeModule" in this instance. For every module that imports the service, Angular will generate a unique instance of the service.
Benefits of providedIn
- Tree-shakable: When Angular's build optimizer uses providedIn, it can eliminate a service that isn't needed in any part of the application. This contributes to a smaller bundle size, which speeds up loading times.
- Lazy loading optimization: Angular will generate a distinct instance of a service for every lazy-loaded module when the service is offered in a particular module. By doing this, encapsulation is maintained and conflicts are avoided and each module is guaranteed to receive its own instance.
- Easier to manage: It is simpler to comprehend where a service is provided and how it functions within an application when the scope of the service is clearly stated.
- Circular dependencies: When working with services that have circular dependencies, exercise caution—especially when offering root-level services. Circular dependencies can cause problems during runtime and complicate debugging the application.
- Accidental multiple instances: Offering a service at the component or lazy-loaded module level could unintentionally result in the creation of several instances of the service. When using providedIn, make sure you are aware of the ramifications of the scope you select.
Conclusion
Effective service dependency management in Angular requires an understanding of providedIn. You may guarantee encapsulation, streamline dependency management, and improve the speed of your Angular application by defining the scope of a service using this property. To prevent unexpected behavior in your application, it's important to be aware of potential risks and use providedIn wisely.