等待RxJS操作-阻止? [英] Wait for RxJS operation - to blocking?

问题描述

我正在使用Angular 4.3.5.我们的应用程序具有可以订阅"用户的程序".我有一个路由器防护功能，如下所示:

I am using Angular 4.3.5. Our app has "programs" that a user can be "subscribed" to. I have a router guard function that looks like this:

canActivate(route: ActivatedRouteSnapshot, state: RouterStateSnapshot) {
    const programName = route.params['program_name'];
    const programId = this.programService.getIdForName(programName);
    if (this.userService.isLoggedIn()  &&  this.subscriptionService.isSubscribed(programId)) {
      return true;
    } else {
      this.router.navigate(['']);
      return false;
    }
}

要获取程序ID，我需要调用服务器.要获取用户的订阅列表并确定他们是否已订阅此特定程序，我需要调用服务器.

To get the program id, I need to call the server. To get the list of subscriptions for the user and determine if they are subscribed to this particular program, I need to call the server.

使用RxJS进行服务器调用是异步的.但是，我的 canActivate 函数被约束为返回布尔值.我不确定如何弥合这种异步/同步编程差距.

The server calls are asynchronous using RxJS. However, my canActivate function is constrained to return a boolean. I am unsure of how to bridge this async/sync programming gap.

例如，在RxJava中，我可以调用 toBlocking()以等待HTTP调用解决.但是RxJS中没有这样的运算符.我已经尝试过 toArray()和 take(1).toArray()[0] ，但是似乎没有任何作用.

In RxJava, for example, I could call toBlocking() to wait for the HTTP call to resolve. But there is no such operator in RxJS. I've tried toArray(), and take(1).toArray()[0], but nothing seems to work.

事实上，我想将这个异步/同步桥降低一些；即我希望 subscriptionService.isSubscribed(programId)返回一个 boolean 而不是一个 Observable< boolean> ，因为我可以缓存订阅列表在 SubscriptionService 中，这样我就不需要每次都调用服务器了；但我认为这不会改变编程的挑战.

In fact, I'd like to push this async/sync bridge down lower; i.e. I want subscriptionService.isSubscribed(programId) to return a boolean instead of a Observable<boolean>, because I can cache the list of subscriptions in the SubscriptionService, so that I don't need to call the server every time; but I don't think that changes the programming challenge.

推荐答案

canActivate 函数可以返回 Observable< boolean> .

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