typescript 两个订阅解析后从服务方法返回 Observable<boolean>

Return Observable<boolean> from service method after two subscriptions resolve

提问by Ben Racicot

I'm trying to setup a simple way to compare the current username with a profile's username within an Angular service.

我正在尝试设置一种简单的方法来将当前用户名与 Angular 服务中的配置文件用户名进行比较。

Obviously the profile username and the user's username must resolve before I can compare them so how do I return a boolean observable so that I can subscribe to this comparison within components?

显然，配置文件用户名和用户的用户名在我可以比较之前必须解析，那么我如何返回一个布尔值 observable 以便我可以在组件内订阅这个比较？

This is where I'm at:

这是我所在的位置：

public profileId = new Subject<string>; // Observable string source updated from a profile.component (when the URL displays the profile's username)
public profileId$ = this.profileId.asObservable();
public currentUser = this.principal.asObservable().distinctUntilChanged();

public isProfileOwner(): Observable<boolean> { // A function whose declared type is neither 'void' nor 'any' must return a value.
    this.currentUser.subscribe(user => {
            this.profileId$.subscribe(
                profile => {
                    console.log(profile + ' ' + user.username); // match!
                    if (profile === user.username) {
                        return Observable.of(true);
                    } else {
                        return Observable.of(false);
                    }
                }
            )
        })
}

This seems to be the way other SO answers explain to do it but I'm getting [ts] A function whose declared type is neither 'void' nor 'any' must return a value.

这似乎是其他 SO 答案解释的方式，但我得到了 [ts] A function whose declared type is neither 'void' nor 'any' must return a value.

I'd like to subscribe to test within components.

我想订阅组件内的测试。

this.authService.isProfileOwner().subscribe(
    data => {
        console.log(data); // should be boolean
    }
)

采纳答案by AJT82

As noticed from other answer by @user184994, forkJoinwon't work in this case. Instead you can use combineLatest, and then very similarily like @user184994 have otherwise implemented the service code:

正如@user184994 从其他答案中注意到的那样，forkJoin在这种情况下不起作用。相反，您可以使用combineLatest, 然后非常相似地像@user184994 以其他方式实现了服务代码：

isProfileOwner(): Observable<boolean> {
  return Observable.combineLatest(this.currentUser, this.profileId$)
    .map(results => {
       let user = results[0];
       let profile = results[1];
       return (user.username === profile)
    });
}

DEMO

演示

回答by Rajani Kanth

This can be achieved through Subject

这可以通过主题来实现

import { Subject } from 'rxjs';

public isProfileOwner(): Observable<boolean> {
        var subject = new Subject<boolean>();

        this.currentUser.subscribe(user => {
                this.profileId$.subscribe(
                    profile => {
                        console.log(profile + ' ' + user.username); // match!
                        if (profile === user.username) {
                            subject.next(true);
                        } else {
                            subject.next(false);

                        }
                    }
                )
            })
            return subject.asObservable();
    }

回答by user184994

I would personally suggest using forkJoin, to wait for the observables, and flatMap to convert to an Observable<boolean>

我个人建议使用forkJoin, 等待 observables 和 flatMap 转换为Observable<boolean>

return Observable.forkJoin(this.currentUser, this.profileId$).flatMap(
    results => {
        user = results[0];
        profile = results[1];
        return Observable.of(profile === user.username)
    }
);