Controllers in NestJS

A controller in NestJS is responsible for handling incoming requests and returning responses to the client. Each controller is associated with a specific route and can handle multiple HTTP methods, such as GET, POST, PUT, PATCH, and DELETE.

Here's a basic example of a controller in NestJS:

import { Controller, Get } from '@nestjs/common'

@Controller('users')
export class UsersController {
  @Get()
  findAll(): string {
    return 'This action returns all users'
  }
}

In this example, the UsersController handles requests to the /users route, and the @Get() decorator defines a route for the HTTP GET method.

Common Decorators in NestJS

NestJS provides a variety of decorators to manage routes, parameters, and responses. Let's take a closer look at some of the most commonly used ones.

@Get(), @Post(), @Put(), @Patch(), and @Delete()

These decorators correspond to the HTTP methods GET, POST, PUT, PATCH, and DELETE, respectively.

import { Controller, Post, Put, Patch, Delete, Get } from '@nestjs/common'

@Controller('products')
export class ProductsController {
  @Get()
  findAll(): string {
    return 'Get all products'
  }

  @Post()
  create(): string {
    return 'Create a product'
  }

  @Put(':id')
  update(@Param('id') id: string): string {
    return `Update product with ID ${id}`
  }

  @Patch(':id')
  partialUpdate(@Param('id') id: string): string {
    return `Partially update product with ID ${id}`
  }

  @Delete(':id')
  remove(@Param('id') id: string): string {
    return `Delete product with ID ${id}`
  }
}

@Body(), @Query(), @Param(), @Headers()

These decorators allow you to easily access request data, such as the body, query parameters, route parameters, and headers.

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

@Controller('orders')
export class OrdersController {
  @Post()
  createOrder(
    @Body() body: any,
    @Query('discount') discount: string,
    @Param('id') id: string,
    @Headers('authorization') authHeader: string
  ): string {
    console.log(body)
    console.log(`Discount: ${discount}`)
    console.log(`Order ID: ${id}`)
    console.log(`Authorization Header: ${authHeader}`)
    return 'Order created'
  }
}

@HttpCode() and @Redirect()

• @HttpCode(): This decorator allows you to specify the HTTP status code of the response.
• @Redirect(): This decorator is used to redirect the client to another URL.

import { Controller, Get, HttpCode, Redirect } from '@nestjs/common'

@Controller('docs')
export class DocsController {
  @Get()
  @HttpCode(200)
  getDocumentation(): string {
    return 'Documentation content'
  }

  @Get('google')
  @Redirect('https://www.google.com', 302)
  redirectToGoogle() {}
}

In the example above, getDocumentation() will return a response with a 200 HTTP status code, while redirectToGoogle() will redirect the client to Google with a 302 status code.