AngularFire2 在注销时取消订阅，在未关闭订阅时出现数据库权限错误

Question

我这里有这段代码使用 AngularFire2 版本，我用它从我的组件之一的数据库中获取一些成员。

当我在同一组件中调用此注销时遇到问题。我取消订阅，但我仍然在控制台中收到错误消息，提示 Exception was thrown by user callback。错误:permission_denied at/users/uid。我知道这是因为我不再登录并且我的数据库规则不允许此读取操作。我不知道为什么我已经退订了，它还在尝试读取数据。

    constructor(private afAuth: AngularFireAuth, private db: AngularFireDatabase) {
        this.user = afAuth.authState;

        this.userSub = this.user.subscribe(auth => {
            if (auth) {
                this.member = db.object('/users/' + auth.uid);
                this.dbSub = this.member.subscribe();
            }
        });
    }

    logout() {
        this.dbSub.unsubscribe();
        this.userSub.unsubscribe();

        this.afAuth.auth.signOut()
            .then(() => this.router.navigateByUrl('/login'));
    }

Answer 1

您或许可以尝试将 RxJS Subject 与运算符 takeUntil() 一起使用，以帮助确保在 signOut() 之前清理可观察对象:

import { Subject } from 'rxjs/Subject';
import 'rxjs/add/operator/takeUntil';

export class Foo {
    private ngUnsubscribe: Subject<void> = new Subject<void>();

    constructor(private afAuth: AngularFireAuth, private db: AngularFireDatabase) {
        this.user = afAuth.authState;

        this.userSub = this.user.subscribe(auth => {
            if (auth) {
                this.member = db.object('/users/' + auth.uid);

                this.dbSub = this.member
                    .takeUntil(ngUnsubscribe)
                    .subscribe(results => console.log(results));
            }
        });
    }

    logout() {
        this.ngUnsubscribe.next();
        this.ngUnsubscribe.complete();

        this.userSub.unsubscribe();

        this.afAuth.auth.signOut()
            .then(() => this.router.navigateByUrl('/login'));
    }
}