constructor(serviceName: string) {
   this.dataSource = Container.instance.get(DataSource);
   this.dataService = this.dataSource.getService(serviceName);
 }

 constructor(private bm: BillingsManager, private ds: DataSource) {
   this.lbService = ds.getService('leistungsblock')
 }

 constructor(private dc: DialogController, ds: DataSource) {
   this.briefeService = ds.getService("briefe");
 }

 public loginAs(name: string, pwd: string) {
   this.ds.login(name, pwd).then(user => {
     if (user) {
       this.session.setUser(user);
       this.router.navigateToRoute("dispatch");
     } else {
       alert("Interner Fehler: Login misslungen");
     }
   });
 }

 public doLogin() {
   this.ds.login(this.username, this.password).then(user => {
     if (user) {
       this.session.setUser(user);
       this.router.navigateToRoute("dispatch");
     } else {
       alert("Username oder Passwort falsch");
     }
   });
 }

 return this.ds.metadata().then(meta => {
   this.testmode = meta.testing;
   return this.ds.login().then(user => {
     if (user) {
       this.session.setUser(user);
       return this.router.navigateToRoute("dispatch");
     } else {
       return true;
     }
   });
 });

 public async login(username?: string, pwd?: string, persist?: boolean) {
   const user: UserType = await this.ds.login(username, pwd);
   if (user) {
     user["type"] = "user";
     this.we.selectItem(user);
     this.currentUser = user;
   } else {
     this.we.logout();
     this.currentUser = undefined;
   }
   return this.currentUser;
 }

 public async logout() {
   this.currentUser = undefined;
   this.we.logout();
   return this.ds.logout();
 }