Response Transform Interceptor for Nest.JS

transform.interceptor.ts

import {
  Injectable,
  NestInterceptor,
  ExecutionContext,
  CallHandler,
} from '@nestjs/common';
import { Observable } from 'rxjs';
import { map } from 'rxjs/operators';

export interface ResponseTemplate<T> {
  message: string;
  data: T;
}

interface Response<T> {
  message: string;
  statusCode: number;
  data: T;
}

@Injectable()
export class TransformInterceptor<T>
  implements NestInterceptor<T, Response<T>>
{
  intercept(
    context: ExecutionContext,
    next: CallHandler,
  ): Observable<Response<T>> {
    return next.handle().pipe(
      map((data: ResponseTemplate<T>) => ({
        message: data.message,
        statusCode: context.switchToHttp().getResponse<{ statusCode: number }>()
          .statusCode,
        data: data.data,
      })),
    );
  }
}