There are two ways to make a service a singleton in Angular:
- Declare that the service should be provided in the application root.
- Include the service in the AppModule or in a module that is only imported by the AppModule.
Beginning with Angular 7.0, the preferred way to create a singleton services is to specify on the service that it should be provided in the application root. This is done by setting providedIn to root on the service’s @Injectable decorator:
src/app/user.service.0.ts
import { Injectable } from ‘@angular/core’;
@Injectable({
providedIn: ‘root’,
})
export class UserService {
}
