Angular-类似于http.get的可观察到的但没有请求

Question

I have this observable http request

refreshToken() {
    return this.http.get(this.siteService.apiDomain() + '/api/token?token=' + localStorage.getItem('JWToken'), {})
        .map((response: Response) => {
            return response;
        })
}

and I'm calling the observable like this

return this.refreshTokenService.refreshToken()
                .flatMap((result: any) => {
                    // if got new access token - retry request
                    if (JSON.parse(result._body).token) {
                        localStorage.setItem('JWToken', JSON.parse(result._body).token);
                    }
                    this.setHeaders(url);
                    return this.request(url, options);
                })

And my problem is that if I have multiple parallel requests I'm making multiple times the refreshToken(). I want to find a way to make a fake http call, and return the token that I already know or nothing.

Observable.empty() // Failed to compile (Type '{}' is not assignable to type 'Response'.)
Observable.empty().filter(() => {return true}) // Compiles but it stop the flatMap sequence.

Answer 1

I'm not sure I completely understand, but maybe you want Observable.of() ?

Here is an example of where I've used it. If the Id is 0, it returns an initialized product as an Observable.

import 'rxjs/add/observable/of';
...

getProduct(id: number): Observable<IProduct> {
    if (id === 0) {
        return Observable.of(this.initializeProduct());
    };
    const url = `${this.baseUrl}/${id}`;
    return this.http.get(url)
        .map(this.extractData)
        .do(data => console.log('getProduct: ' + JSON.stringify(data)))
        .catch(this.handleError);
}

Answer 2

I would recommend use of BehaviourSubjects, Its will allow you to store the last value until either the component destroyed or you face it to change. Also when the value changes on the BehaviourSubject; every component that have subscribe to it also recieves new data. Plus as a added bonus you dont need to call the server evrytime a component want to get the value like Observable, since its storing the value, you can get the value anytime without calling the server. BehaviourSebject example