javascript - Angular 4.3 HttpClient : Intercept response

Question

In the documentation about the new HttpClientModule included in the new version of Angular 4.3, the mechanism to intercept requests is explained very well. There is also mention of the response interceptor mechanism however I cannot find anything about it.

Does anyone have an idea about how to intercept a response in order to modify the body message before it is sent to the service?

Thanks.

Answer 1

I recently made an HttpInterceptor in order to resolve cyclical references in some JSON on the client side, essentially replacing any object with a $ref property with the object in the JSON that has a matching $id property. (This is the output you get if Json.Net is configured with PreserveReferencesHandling.Objects and ReferenceLoopHandling.Ignore).

The answers here helped me some of way, but none of them show how to modify the body of the response, like the OP needs. In order to do so, one needs to clone the event and update the body, like so:

intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
    return next.handle(req).map(event => {
        if (event instanceof HttpResponse && shouldBeIntercepted(event)) {
            event = event.clone({ body: resolveReferences(event.body) })
        }         
        return event;
    });
}

Any event that should not be modified is simply passed through to the next handler.