CODEWITHSUNDEEP
angular
Devesh Jadon
Devesh Jadon

Reputation: 7464

Difference between Injectables and Observables?

I have been working upon my new Angular2 app and is confused between Injectables and Observables?

Upvotes: 0

Views: 831

Answers (1)

Günter Zöchbauer
Günter Zöchbauer

Reputation: 657406

These two aren't related in any way. You can use Observables in Injectables like anywhere else, but that's about it.

An Observable is similar what is known as Stream in other languages. An Observable can be subscribed to and when it emits events, subscriber get notified. Observable is a bit like Promise but for a possible series of values instead just one value.

Injecable is a class that can be instantiated and injected by Angulars DI. (dependency injection). When a class has a decorator like

@Injectable() 
export class SomeClass {
  constructor(private http:Http) {}
}

and some other class (for example an Angular2 component) like

@Component({...}
export class MyComponent {
  constructor(private someClass:SomeClass) {}
}

that is instantiated by Angulars DI, DI inspects the constructor parameters and looks up injectables that match the constructor parameter declaration, creates a new instance (in this case of SomeClass), but because SomeClass also has a constructor parameter, DI first has to look up or create a new instance of Http to be able to pass it to SomeClass.

An Injectable therefore is a class that can be instantiated by DI:

Upvotes: 4

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