**Course Title:** Mastering NestJS: Building Scalable Server-Side Applications **Section Title:** Controllers and Routing **Topic:** Understanding routing and route parameters In this topic, we will delve into the world of routing in NestJS, exploring how to define routes, handle route parameters, and create a robust routing system for your applications. ### What is Routing in NestJS? Routing is the process of mapping URLs to specific controller methods in your NestJS application. It allows you to define how your application responds to different HTTP requests, such as GET, POST, PUT, and DELETE. ### Defining Routes in NestJS To define a route in NestJS, you need to use the `@Controller` decorator and specify the route path using the `@Get`, `@Post`, `@Put`, `@Delete`, or other decorators. Here's an example: ```typescript import { Controller, Get } from '@nestjs/common'; @Controller('users') export class UsersController { @Get() findAll(): string { return 'This is the list of all users'; } } ``` In this example, we've defined a `UsersController` with a single method `findAll` that returns a string. The `@Get` decorator specifies that this method should be called when the `/users` route is accessed. ### Route Parameters Route parameters allow you to pass data from the URL to your controller methods. You can define route parameters using the `:parameterName` syntax in your route path. Here's an example: ```typescript import { Controller, Get } from '@nestjs/common'; @Controller('users') export class UsersController { @Get(':id') findOne(@Param('id') id: string): string { return `This is the user with id ${id}`; } } ``` In this example, we've defined a `findOne` method that takes a `id` parameter. The `@Param` decorator is used to inject the value of the `id` parameter from the URL. ### Path Parameters vs. Query Parameters Path parameters are values that are passed in the URL path, while query parameters are values that are passed in the URL query string. Here's an example: ```typescript import { Controller, Get } from '@nestjs/common'; @Controller('users') export class UsersController { @Get(':id') findOne(@Param('id') id: string): string { return `This is the user with id ${id}`; } @Get() findAll(@Query('name') name: string): string { return `This is the list of users with name ${name}`; } } ``` In this example, we've defined two methods: `findOne` with a path parameter `id`, and `findAll` with a query parameter `name`. ### Conclusion In this topic, we've covered the basics of routing in NestJS, including defining routes, handling route parameters, and creating a robust routing system for your applications. We've also explored the difference between path parameters and query parameters. ### Practical Takeaways * Use the `@Controller` decorator to define a controller and specify the route path. * Use the `@Get`, `@Post`, `@Put`, `@Delete`, or other decorators to define routes and specify the HTTP method. * Use the `@Param` decorator to inject route parameters into your controller methods. * Use the `@Query` decorator to inject query parameters into your controller methods. ### Next Topic In the next topic, we will cover "Handling HTTP requests and responses" in NestJS. ### Leave a comment or ask for help If you have any questions or need help with implementing routing in your NestJS application, please leave a comment below.