Combining 2 Observables in nestjs Interceptor: A Step-by-Step Guide

Question

Combining 2 Observables in nestjs Interceptor: A Step-by-Step Guide

I am currently working on a NestJS interceptor to geolocate an address that is being sent through a REST API. Here is the code snippet:

export class PointsInterceptor implements NestInterceptor {
  intercept(context: ExecutionContext, next: CallHandler): Observable<any> {

    var myAddress = context.switchToHttp().getRequest().body;
    const geoCodingObservable = from(geocoder.geocode(myAddress));
    geoCodingObservable.subscribe(value => console.log(JSON.stringify(value)));

    return next.handle().pipe(map(value => console.log(value)))
  }

}

The output of this code includes:

a JSON object from the HTTP response:

{
  address: '123, Avenue des Champs Elysées, 75008 PARIS',
  _id: new ObjectId("64bd089088f925780705bbbd"),
  __v: 0
}

An object obtained from the geoCoder

[{"latitude":48.872438,"longitude":2.29811,"state":"75, Paris, Île-de-France","city":"Paris","zipcode":...}]

My goal is to combine all this information into a single JSON object that can be "pushed to the database". I have tried using merge and mergeWith, but without success.

Any assistance on this matter would be highly appreciated.

Thank you.

typescript rxjs nestjs

Answer 1

Answer №1

Have you ever considered using the tap method? Instead of subscribing, try utilizing from and then performing a tap on both operations. Please note that this approach has not been tested.

export class PointsInterceptor implements NestInterceptor {
  intercept(context: ExecutionContext, next: CallHandler): Observable<any> {
    const monaddress = context.switchToHttp().getRequest().body;
    const geocodeResult = from(geocoder.geocode(monaddress));
    const geoCoder = await lastValueFrom(geocodeResult);

    return next.handle().pipe(
      tap(value => console.log(value)),
      map(value => {
        //1: Returning objects from both next.handle() and geoPremiseToObservable
        return {
          httpResponse: value,
          geoCoder: geoCoder
        };

       //2: Merging the geocoder response with the http response into a single object
        return {
          ...value,
          geoCoder: geoCoder
        };
      })
    );
  }
}

Answer 2

Have you ever considered using the tap method? Instead of subscribing, try utilizing from and then performing a tap on both operations. Please note that this approach has not been tested.

export class PointsInterceptor implements NestInterceptor {
  intercept(context: ExecutionContext, next: CallHandler): Observable<any> {
    const monaddress = context.switchToHttp().getRequest().body;
    const geocodeResult = from(geocoder.geocode(monaddress));
    const geoCoder = await lastValueFrom(geocodeResult);

    return next.handle().pipe(
      tap(value => console.log(value)),
      map(value => {
        //1: Returning objects from both next.handle() and geoPremiseToObservable
        return {
          httpResponse: value,
          geoCoder: geoCoder
        };

       //2: Merging the geocoder response with the http response into a single object
        return {
          ...value,
          geoCoder: geoCoder
        };
      })
    );
  }
}

Combining 2 Observables in nestjs Interceptor: A Step-by-Step Guide

Answer №1

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