angular – 如何从subscribe返回observable

发布时间：2020-12-17 08:02:29 所属栏目：安全来源：网络整理

导读：当我在订阅者中获得某个值时，我正试图返回一个observable，但我失败了。这是代码： canActivate(route: ActivatedRouteSnapshot,state: RouterStateSnapshot):Observableboolean { // get route to be activated this.routeToActivate = route.routeConfig

当我在订阅者中获得某个值时，我正试图返回一个observable，但我失败了。

这是代码：

canActivate(route: ActivatedRouteSnapshot,state: RouterStateSnapshot):Observable<boolean> {
    // get route to be activated
    this.routeToActivate = route.routeConfig.path;

    // get user access levels        
    return this._firebase.isUserAdmin          <-- returns Subscription,not Observable
        .map(user => user.access_level)
        .subscribe( access => {
           // I need to return an observable here
        });
}

角度2中的可观察量资源不多，所以我不知道从哪里开始。有人可以帮忙吗？

更新 – >工作版

canActivate(route: ActivatedRouteSnapshot,state: RouterStateSnapshot):Observable<boolean> {
            // get route to be activated
            this.routeToActivate = route.routeConfig.path;

            // get user access levels        
            return this._firebase.isUserAdmin
                .map(user => {
                    let accessLevel = user.access_level;

                    if (accessLevel === 'admin' ) {
                        return true;
                    }

                }).first();
        }

您无法从订阅返回observable，但如果您使用map而不是subscribe，则返回Observable。

canActivate(route: ActivatedRouteSnapshot,state: RouterStateSnapshot):Observable<boolean> {
    // get route to be activated
    this.routeToActivate = route.routeConfig.path;

    // get user access levels        
    return this._firebase.isUserAdminObservable
        .map(user => {
           // do something here
           // user.access_level;
           return true;
         })
        .first(); // for the observable to complete on the first event (usually required for `canActivate`)
        // first needs to be imported like `map`,...
}

canActivate(route: ActivatedRouteSnapshot,state: RouterStateSnapshot):Observable<boolean> {
    // get route to be activated
    this.routeToActivate = route.routeConfig.path;

    let subject = new Subject();
    // get user access levels        
    this._firebase.isUserAdminObservable
        .map(user => {
          let accessLevel = user.access_level; 
          if (accessLevel === 'admin' ) { 
            subject.emit(true); 
            subject.complete();
          } 
          return user;
        });
     return subject;
}

（编辑：李大同）

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