我有一个需要观察到的值来发出两个值的情况。应该立即发出第一个值,并且所有订户应立即获得该值。第二个值可能需要一些时间,但所有订户也应获得该值。
目前,我是这样做的:
import {Observable} from 'rxjs';
import {tap, startWith} from 'rxjs/operators';
@Injectable()
export class CacheInterceptor implements HttpInterceptor {
intercept(req: HttpRequest<any>, next: HttpHandler) {
const cachedResponse = cache.get(req);
const results$ = sendRequest(req, next);
return cachedResponse ? results$.pipe(startWith(cachedResponse)) : results$;
}
}
function sendRequest(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
return next.handle(req).pipe(
tap(event => {
if (event instanceof HttpResponse) {
cache.put(req, event);
}
})
);
}
export class HttpCache {
cache = new Map();
get(req: HttpRequest<any>): HttpResponse<any> | undefined {
// ...
}
put(req: HttpRequest<any>, response: HttpResponse<any>): void {
// ...
}
}
const cache: HttpCache = new HttpCache();
如您所见,我尝试做results$.pipe(startWith(cachedResponse))
。
似乎发生的事情是我总是发出results$
值,而从未发出cachedResponse
值。任何帮助将不胜感激。