Nest: [Suggestion] - add simplified class for interceptor

Created on 27 Oct 2017 · 11Comments · Source: nestjs/nest

Hi,
I think it would be great to have a simplified version of the interceptor mechanism, which will use the current implementation.

I suggest to create a base interceptor class, which will look like so:

export abstract class BaseInterceptor implements NestInterceptor {
  protected onBefore(request?: any) {
  }

  protected onAfter(data?: any) {
  }

  intercept(dataOrRequest: any, context: ExecutionContext, stream$: Observable<any>): Observable<any> {
    this.onBefore(dataOrRequest);

    return stream$.map((data) => {
      return this.onAfter(data);
    });
  }
}

And here is how the LoggingInterceptor will look:

@Interceptor()
export class LoggingInterceptor extends BaseInterceptor {
  onBefore(request: any) {
    console.log('Before...');
  }

  onAfter(data) {
    console.log('After...');

    return data;
  }
}

The benefit of this implementation is the simplified (in my opinion) API that it brings, WDYT?

Note: it would be even better if there we different mechanism for interception when it will require an interceptor to implement the onBefore and onAfter interfaces. This way inheritance won't be needed.

discussion 🔥 todo 💚

Source

vlio20

👍4

Most helpful comment

@wbhob, @kamilmysliwiec can I PR?

vlio20 on 11 Nov 2017

👍5

All 11 comments

Would be more than happy to submit a PR for that if you think this is valuable.

vlio20 on 27 Oct 2017

This would require some refactoring on the internals of Nest, but I like this API. It is important, however, to keep the intercept method intact, for more advanced users.

wbhob on 28 Oct 2017

Hi @vlio20,
I know that the current interceptor API may be confusing a little, but the reason why we're using rxjs streams are their capabilities. The interceptors have a lot of use cases, not only the aspects things like after / before execution hooks so I'm not going to change them. What I think is that it would be great to have a base class (same as in your example) for less advanced users, so they can extend and override methods (onBefore & onAfter), but the best place for this class would be a utils repository (more here). Thanks!