How to check if the value was saved

Ionic Framework ionic-v3
8

I would use a shared service for this.

interface User {
  phone: string;
  // whatever else
}

LoginPage {
  constructor(private _auth: AuthService, private _uisvc: UserInfoService, private _nav: NavController) {}
  login(): void {
    this._uisvc.getUserInfo(this.form.whatever).subscribe((ui) => {
      this._auth.user = ui;
      this._nav.push(DashboardPage);
    });
  }
}

AnyOtherPage {
  constructor(private _auth: AuthService) {}
  doSomething(): void {
    relyOn(this._auth.user);
  }
}

AuthService {
  user: User;
}

UserInfoService {
  constructor(private _http: Http) {}
  getUserInfo(whatever): Observable<User> {
    return this._http.get(url + whatever).map(rsp => rsp.json());
  }
}

My personal preference when dealing with login/logout is to handle it all in a subscription in the app component, so I never deal with the NavController at all. Details here if you want to consider that approach.