Create a ToDo Item Provided from the Request Body

Welcome to this lesson on creating a ToDo item provided from the request body using NestJS. So far, you have learned how to handle GET requests to fetch all ToDo items and fetch a single ToDo item by its ID. In this lesson, we'll expand on that by focusing on how to create a new ToDo item using a POST request. We will dive into the details of the controller and service layers, as well as using Data Transfer Objects (DTOs).

A POST request is a type of HTTP request method used within the context of RESTful APIs to send data to a server to create a new resource. In REST architecture, POST requests are utilized to submit data enclosed in the request body (as opposed to data in the URL) to a specified endpoint, which processes the data and creates a new resource. This method is typically used to create new entries in a database, such as adding a new Todo item to a Todo list. The server then processes this information and often responds with a representation of the newly created resource, including any additional data the server has added, like a unique identifier.

Unlike GET requests, which retrieve data, POST requests send data within the request body to a server endpoint, where it is processed and used to create a new resource, such as adding a new Todo item to a list. While a GET request might fetch the current list of Todo items or details of a specific item, a POST request is used to submit new information, like a new task, which the server stores in the database. We often like to talk in the terms of mutating (changing) data. In a REST API, it is typical for GET requests to query data but not mutate it. POST requests (and similar PUT and DELETE requests which we'll learn about in the next lesson) mutate the data. Because of this, you'll often hear people refer to queries and mutations in an API.

The controller in our NestJS application handles incoming HTTP requests and sends responses. In this case, the TodoController will manage our POST requests for creating new ToDo items.

Here’s a detailed breakdown of the provided TodoController code snippet:

@Controller('todos')
export class TodoController {
  constructor(private readonly todoService: TodoService) {}

  // ... Existing GET handlers

  @Post() // Decorate the create method to declare that this handles POST requests
  create(
    // Decorate this data object with @Body() to declare that the data comes
    // from the HTTP body and not the URL
    @Body() todo: CreateTodoDto,
  ): TodoDto {
    return this.todoService.createTodo(todo);
  }
}

This controller sets up our route to handle the creation of ToDo items.