如何创建像Angular1服务这样的单例对象？

Question

I am wondering how can I create singleton object in Angular2, that will hold the value of some attributes throughout life of application - so that I can use it in many components, and inject it.

Any ideas?

Thanks

My attempt was to do:

bootstrap(MyApp,[ROUTER_PROVIDERS,
HTTP_PROVIDERS,
provide(LocationStrategy, {useClass: HashLocationStrategy}),
provide(APP_BASE_HREF, {useValue: '/'}),Login])

where 

Login:

@Injectable()
export class Login {
    public  username: string = "any";
    constructor(private _http:Http, private _router:Router){

    }

    public static login(username,password){
        var creds = 'username=' + username+'&password='+password;
        this._http.post('/authentication/login',creds,{headers: contentHeaders})
            .subscribe(
                success =>{
                    this.username = success.json().username;
                    this._router.navigate(['Dashboard']);
            },
                error =>{
                    console.log('Wrong creds')
            });
    }

    public getUsername(){
        return this.username;
    }
}

In this case, getUsername() works, but this._http post does not - it throws an error:

ORIGINAL EXCEPTION: TypeError: Cannot read property 'post' of undefined ORIGINAL STACKTRACE:

Answer 1

singleton pattern can be achieved through sharedService . You have to inject it into bootstrap function like

bootstrap(AppComponent,[sharedService]); // 

I have read your updated question. Plunker which shares object like you want.

Answer 2

Add the service to the providers list in

bootstrap(AppComponent, [OtherProviders, MySingletonService]);

(don't add MySingletonService anywhere else to providers .

Angular2 DI ensures that the same instance is injected everywhere.