Implementing Update and Delete Handlers in NestJS

Welcome to the lesson on implementing the Update and Delete handlers in a Todo REST API with NestJS. In this lesson, we'll build upon what we've learned so far to complete the CRUD functionality in our application.

Previously, you set up GET queries to fetch all Todo items or a specific item by its ID and implemented the POST handler to create new Todo items. Now, we'll focus on how to update and delete Todo items using PUT and DELETE requests, respectively.

In RESTful web services, HTTP methods (also known as verbs) play a crucial role in defining the actions that can be performed on resources. We've learned about GET and POST. Two key methods we will focus on in this lesson are PUT and DELETE.

• PUT: The PUT method is used to update the state of a resource. If the resource does not exist, PUT can also create a new resource with the specified data, although this behavior can vary depending on implementation. In our implementation, we will not create a record via PUT if it does not already exist.
• DELETE: The DELETE method is used to remove a resource. After a successful DELETE request, the resource should no longer exist on the server.

In NestJS, controllers handle incoming HTTP requests and send responses to the client. They typically delegate the business logic to services. For this lesson, we'll extend our TodoController to include methods for updating and deleting Todo items.

Here's the basic structure of our updated TodoController:

import { Controller, Put, Delete, Param, Body } from '@nestjs/common';
import { TodoService } from './todo.service';
import { UpdateTodoDto } from './dtos/update-todo.dto';

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

  // ... POST and GET handlers removed for brevity

  // Decorate the PUT handler to require the ID in the URL for PUT /todos/:id
  @Put(':id')
  update(
    // Decorate the id parameter to declare that it comes from the URL
    @Param('id') id: string,
    
    // Decorate the todo parameter to declare that it comes from the body of the request
    @Body() todo: UpdateTodoDto,
  ) {
    return this.todoService.updateTodo(id, todo);
  }

  // Decorate the DELETE handler to require the ID in the url for DELETE /todos/:id
  @Delete(':id')
  remove(
    // Decorate the id parameter to declare that it comes from the URL
    @Param('id') id: string,
  ) {
    return this.todoService.deleteTodo(id);
  }
}