**Course Title:** Mastering NestJS: Building Scalable Server-Side Applications **Section Title:** Controllers and Routing **Topic:** Creating and configuring controllers in NestJS In this topic, we will delve into the world of controllers in NestJS, exploring how to create and configure them to handle incoming requests and return responses. By the end of this topic, you will have a solid understanding of how to create controllers, inject dependencies, and handle different types of requests. ### What are Controllers in NestJS? In NestJS, a controller is a class that handles incoming requests and returns responses. It is the entry point for HTTP requests and is responsible for interacting with the business logic of your application. Controllers are typically decorated with the `@Controller` decorator, which specifies the base path for the controller methods. ### Creating a Controller To create a controller, you need to create a new class that will handle incoming requests. Here's an example of a simple controller: ```typescript // app/controllers/example.controller.ts import { Controller, Get } from '@nestjs/common'; @Controller('example') export class ExampleController { @Get() getHello(): string { return 'Hello World!'; } } ``` In this example, we've created a controller called `ExampleController` that handles GET requests to the `/example` path. The `getHello` method returns a simple string response. ### Injecting Dependencies Controllers can inject dependencies using the `@Inject` decorator. Here's an example of a controller that injects a service: ```typescript // app/controllers/example.controller.ts import { Controller, Get, Inject } from '@nestjs/common'; import { ExampleService } from './example.service'; @Controller('example') export class ExampleController { constructor(private readonly exampleService: ExampleService) {} @Get() getHello(): string { return this.exampleService.getHello(); } } ``` In this example, we've injected the `ExampleService` into the controller using the `@Inject` decorator. We can then use the service in the `getHello` method. ### Handling Different Types of Requests Controllers can handle different types of requests using various decorators. Here are a few examples: * `@Get()`: Handles GET requests * `@Post()`: Handles POST requests * `@Put()`: Handles PUT requests * `@Delete()`: Handles DELETE requests * `@Patch()`: Handles PATCH requests Here's an example of a controller that handles different types of requests: ```typescript // app/controllers/example.controller.ts import { Controller, Get, Post, Put, Delete, Patch } from '@nestjs/common'; @Controller('example') export class ExampleController { @Get() getHello(): string { return 'Hello World!'; } @Post() createHello(): string { return 'Hello World!'; } @Put() updateHello(): string { return 'Hello World!'; } @Delete() deleteHello(): string { return 'Hello World!'; } @Patch() patchHello(): string { return 'Hello World!'; } } ``` In this example, we've created a controller that handles different types of requests using various decorators. ### Conclusion In this topic, we've covered the basics of creating and configuring controllers in NestJS. You've learned how to create controllers, inject dependencies, and handle different types of requests. By following the examples and code snippets provided, you should be able to create your own controllers and start building scalable server-side applications with NestJS. ### What's Next? In the next topic, we'll explore the world of routing and route parameters in NestJS. You'll learn how to create routes, inject route parameters, and handle different types of requests using route parameters. ### Leave a Comment or Ask for Help If you have any questions or need help with creating controllers in NestJS, please leave a comment below. I'll do my best to assist you. ### External Resources * NestJS Documentation: [Controllers](https://docs.nestjs.com/controllers) * NestJS Documentation: [Routing](https://docs.nestjs.com/routing) * NestJS GitHub Repository: [Controllers](https://github.com/nestjs/nest/tree/master/packages/common/src/controllers) * NestJS GitHub Repository: [Routing](https://github.com/nestjs/nest/tree/master/packages/common/src/routing)