[AngularFire2] Signup and logout

import {AuthProviders, FirebaseAuthState, FirebaseAuth, AuthMethods} from "angularfire2";import {Injectable} from "@angular/core";import {Subject, BehaviorSubject} from "rxjs";import {AuthInfo} from "./AuthInfo";

@Injectable()export class AuthService {

  static UNKNOW_USER = new AuthInfo(null);

  private authState: FirebaseAuthState = null;  public authInfo$: BehaviorSubject<AuthInfo> = new BehaviorSubject<AuthInfo>(AuthService.UNKNOW_USER);

  constructor(public auth$: FirebaseAuth) {    auth$.subscribe((state: FirebaseAuthState) => {      this.authState = state;    });  }

  signUp(email, password){    return this.fromFirebaseAuthPromise(this.auth$.createUser(      {email, password}    ));  }

  login(email, password) {

    return this.fromFirebaseAuthPromise(this.auth$.login({      email, password    },{      method: AuthMethods.Password,      provider: AuthProviders.Password    }));  }

  logout(){    this.auth$.logout();    this.authInfo$.next(AuthService.UNKNOW_USER);  }

  fromFirebaseAuthPromise(promise) {    const subject = new Subject<any>();

    promise.then((res) => {      const uid = this.authState.uid;      const authInfo = new AuthInfo(uid);      this.authInfo$.next(authInfo);      subject.next(res);      subject.complete();    }, err => {      this.authInfo$.error(err);      subject.error(err);      subject.complete();    });

    return subject.asObservable();  }}