NestInterceptor

Kind: Interface

Source: packages/common/interfaces/features/nest-interceptor.interface.ts

Part of: Common

Interface describing implementation of an interceptor.

NestInterceptor defines a hook for wrapping and transforming request handling in NestJS. Implementations receive the current ExecutionContext and a CallHandler, allowing them to run logic before or after the route handler, modify responses, handle errors, or measure execution time.

Diagram

mermaid
graph LR
  A[Incoming Request] --> B[Interceptor.intercept]
  B --> C[ExecutionContext]
  B --> D[CallHandler]
  D --> E[Route Handler]
  E --> F[Observable Response]
  F --> G[Interceptor Response Transformation]
  G --> H[Client Response]

Usage

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

@Injectable()
export class ResponseEnvelopeInterceptor implements NestInterceptor {
  intercept(
    context: ExecutionContext,
    next: CallHandler,
  ): Observable<{ data: unknown }> {
    return next.handle().pipe(
      map((data) => ({ data })),
    );
  }
}

// Register globally or attach to a controller/route:
// @UseInterceptors(ResponseEnvelopeInterceptor)

AI Coding Instructions

• Implement intercept(context, next) and always return an Observable from next.handle() unless intentionally short-circuiting the request.
• Use RxJS operators such as map, catchError, tap, and finalize to transform responses, handle errors, or perform side effects.
• Use ExecutionContext to access transport-specific details, such as context.switchToHttp().getRequest() for HTTP requests.
• Register interceptors with @UseInterceptors(), as global interceptors, or through dependency injection when they require application services.
• Avoid subscribing to next.handle() inside the interceptor; return the observable so Nest can manage the response lifecycle.

Used by

36 references from 36 files. Each is a place in this repository where the symbol is actually used — go read one rather than trusting an example.

Imported by (36)

• DataInterceptor — integration/graphql-code-first/src/common/interceptors/data.interceptor.ts:10
• Interceptor — integration/inspector/src/circular-hello/interceptors/logging.interceptor.ts:10
• TimeoutInterceptor — integration/inspector/src/common/interceptors/timeout.interceptor.ts:10
• LoggingInterceptor — integration/inspector/src/core/interceptors/logging.interceptor.ts:10
• TransformInterceptor — integration/inspector/src/core/interceptors/transform.interceptor.ts:14
• LoggingInterceptor — integration/inspector/src/request-chain/interceptors/logging.interceptor.ts:10
• PassthroughInterceptor — integration/nest-application/sse/src/app.controller.ts:28
• Interceptor — integration/scopes/src/circular-hello/interceptors/logging.interceptor.ts:10

…and 28 more.