PipesConsumer

Kind: Class

Source: packages/core/pipes/pipes-consumer.ts

Part of: Core

PipesConsumer is NestJS core infrastructure that executes a sequence of PipeTransform instances against an argument value. It applies pipes in declaration order, passing each transformed result to the next pipe along with normalized argument metadata.

Methods

Diagram

mermaid
graph LR
  A[Route argument value] --> B[PipesConsumer.apply]
  B --> C[Normalize ArgumentMetadata]
  C --> D[applyPipes]
  D --> E[Pipe 1 transform]
  E --> F[Pipe 2 transform]
  F --> G[Additional pipes]
  G --> H[Transformed value]

Usage

ts
import { PipeTransform, ArgumentMetadata } from '@nestjs/common';
import { PipesConsumer } from '@nestjs/core/pipes/pipes-consumer';

class TrimPipe implements PipeTransform<string, string> {
  transform(value: string, metadata: ArgumentMetadata): string {
    if (metadata.type === 'body' && typeof value === 'string') {
      return value.trim();
    }

    return value;
  }
}

async function transformInput() {
  const pipesConsumer = new PipesConsumer();

  const result = await pipesConsumer.apply(
    '  NestJS  ',
    {
      type: 'body',
      data: undefined,
      metatype: String,
    },
    [new TrimPipe()],
  );

  console.log(result); // "NestJS"
}

AI Coding Instructions

• Preserve sequential pipe execution: every pipe must receive the resolved output of the previous pipe.
• Use apply() when working with Nest route argument metadata; it normalizes route parameter types before calling applyPipes().
• Ensure custom pipes implement PipeTransform and return either a transformed value or a Promise resolving to one.
• Do not bypass pipe errors; validation and transformation exceptions should propagate to Nest’s exception handling flow.
• Treat PipesConsumer as core framework infrastructure; application code should usually configure pipes with decorators or global pipe registration instead of invoking it directly.

How it works

PipesConsumer

PipesConsumer is a core class that runs an input value through an ordered array of PipeTransform instances, passing argument metadata to every transform. Its apply() method accepts framework route-parameter metadata, while applyPipes() accepts metadata with a direct type value. [packages/core/pipes/pipes-consumer.ts:5-28]

Relationships

• IMPORTS → RouteParamtypes
• IMPORTS → ArgumentMetadata
• IMPORTS → PipeTransform

Used by

4 references from 4 files. Each is a place in this repository where the symbol is actually used — go read one rather than trusting an example.

Imported by (4)

• RpcHandlerMetadata — packages/microservices/context/rpc-context-creator.ts:35
• MicroservicesModule — packages/microservices/microservices-module.ts:23
• WsHandlerMetadata — packages/websockets/context/ws-context-creator.ts:34
• SocketModule — packages/websockets/socket-module.ts:27