NestJS Request | Param, Body, Query, Headers, IP

In NestJS, decorators are used to define metadata for various aspects of your application, including request handling. Let's break down each of the decorators for handling a NestJS Request.

1. @Param(key?: string)

• Description: This decorator is used to extract parameters from the request URL.

  • Usage: It can be applied to method parameters in a controller class to capture specific parameters from the URL.

    Example:

 @Get('/param/:id')
  getParam(@Param('id') id: string) {
    return `Param ID: ${id}`;
  }

In this example, the :id in the route will be captured and passed to the getParam method.

2. @Body(key?: string)

• Description: Used to extract data from the request body.

  • Usage: Apply it to a method parameter to receive data from the body of a POST or PUT request.

    Example:

   @Post()
  postBody(@Body() body: any) {
    return `Body Data: ${JSON.stringify(body)}`;
  }

This example expects a JSON object with a key data in the request body.

3. @Query(key?: string)

• Description: Extracts parameters from the query string in the URL.

• Usage: Apply it to a method parameter to capture query parameters.

  Example:

  @Get()
  getQuery(@Query() query: any) {
    return `Query Parameter:${JSON.stringify(query)}`;
  }

If the URL is /example?name=hasabTech, the getQuery method will receive {name=:hasabTech}

4. @Headers(name?: string)

• Description: Extracts values from the request headers.

• Usage: Apply it to a method parameter to get a specific header value.

  Example:

      @Get('/header/')
      getHeaders(@Headers() headers: any) {
        return `Header: ${JSON.stringify(headers)}`;
      }
  

  This example extracts the value of the authorization header.

5. @Ip()

• Description: Retrieves the client's IP address from the request.

• Usage: Apply it to a method parameter to get the client's IP.

  Example:

     @Get('ip')
      getIp(@Ip() ip: string) {
        return `Client IP: ${ip}`;
      }
  

  This example retrieves the IP address of the client making the request.

Complete Controller Code

import {
  Body,
  Controller,
  Get,
  Ip,
  Param,
  Post,
  Query,
  Headers,
} from '@nestjs/common';

@Controller('request')
export class RequestController {
  @Get('/param/:id')
  getParam(@Param('id') id: string) {
    return `Param ID: ${id}`;
  }

  @Post()
  postBody(@Body() body: any) {
    return `Body Data: ${JSON.stringify(body)}`;
  }

  @Get()
  getQuery(@Query() query: any) {
    return `Query Parameter:${JSON.stringify(query)}`;
  }

  @Get('/header/')
  getHeaders(@Headers() headers: any) {
    return `Header: ${JSON.stringify(headers)}`;
  }

  @Get('ip')
  getIp(@Ip() ip: string) {
    return `Client IP: ${ip}`;
  }
}

These decorators simplify the process of handling different parts of the HTTP request in your NestJS application by providing a clean and structured way to access request parameters, body, headers, IP address, and host parameters.

If you’re a visual learner, check out the following video tutorial for this blog:

https://www.youtube.com/watch?v=0EuhRfJn0Aw&embeds_referring_euri=https%3A%2F%2Fdev.to%2F&source_ve_path=MjM4NTE

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