angular - Angular2 global service provider

Question

/app
        - app.component.ts 
        - app.component.html (hide/show: menu bar)
        - app.global.service.ts (Public varible LoginSuccess:boolean)
        - main.ts
        /student
            - student.ts
            - student.service.ts
            - student.component.ts
            - student.component.html
        /security
            - login.component.ts (LoginSuccess = true)
            - login.component.html

In my application of Angular2, I have a simple need where I want to show hide menu bar based on login success. For that I created a service which just have a LoginSuccess boolean varilable, which I would set on login component and will use on app.component.html for [hidden]=LoginSuccess nav tag.

Problem I am facing is, even after injecting app.global.service.ts thru constructor of app.component.ts & login.component.ts value is not persisting and each constructor creating new object of app.global.service.ts.

Question: How can I achieve to persist single value across application thru service. Somewhere in Angular2 docs, I did read that Injectable service is singleton.

Answer 1

You should provide GlobalService at bootstrap, and not for each component:

bootstrap(AppComponent, [GlobalService])

@Component({
  providers: [], // yes
  // providers: [GlobalService], // NO.
})
class AppComponent {
  constructor(private gs: GlobalService) {
    // gs is instance of GlobalService created at bootstrap
  }
}

This way GlobalService will be a singleton.

For more advanced approach see this answer.