Angular Services

Angular Services

What are Angular Services Angular Service Scope Angular Provider Scope Angular Singleton Services Angular Dependency Injection

Angular Dependency Injection

Dependency Injection (DI) is a pattern in which a class gets its dependent classes from an external source/framework instead of instantiating them within the class.  Dependency Injection makes an application easy to maintain and makes testing easier, since the dependent objects are injected from outside we can use Mock objects to test the behavior of a class when the actual object is not ready for testing.

Angular Singleton Services

A Singleton Service is one which has only one instance shared across the entire Angular App, it is a great way to share data across different components even if they don’t have any Hierarchal relationship. Services can be declared Singleton by setting the providedIn property of the @Injectable() to "root", when creating the service.

@Injectable({
  providedIn: 'root',
})

Angular Provider Scope

In the previous post, we saw on how to make a service available globally by declaring the @Injectable providedIn: 'root'. We can also declare module-level services using ProvidedIn, in this post we shall see on how to declare module-level service using @Injectable

To limit the scope of a service to a module we need to specify the module in the providedIn instead of ‘root’. In the below code the HellpService is made available only to the HelloModule, the service is not available to any other Modules in the Application.

Angular Service Scope

In Angular, Services are a great way to share information among Components that don't know each other. Based on how we register a service we can control the scope/visibility of the service across the Application.

Services can be registered with 3 levels of scope
1. Global Scope
2. Module Scope
3. Component Scope

What are Angular Services?

 In Angular, a Service is a class that is used to provide shared features across different components. Components are the View layer they deal only with UI specific features. Functional tasks like ajax calls, business logic, validations, logging, etc are delegated to the services.

Services are a great way to share information among Components that don't know each other. Based on how we register a service we can control the scope / visibility of the service across the Application. Services can be registered with 3 levels of scope

1. Global Scope
2. Module Scope
3. Component Scope