Hello, Nest

Part of the TypeScript and NestJS section of Coddy's Node.js journey. Lesson 2 of 24.

In Express every route is a function you register by hand. NestJS gives each part of an API its own class, and decorators tell Nest what each class does.

@Controller('books')
export class BooksController {
    @Get()
    findAll() {
        return [{ title: 'Dune' }];
    }
}

A controller answers the requests for one path. @Controller('books') and @Get() are decorators. A decorator starts with @ and sits on the line above a class or a method, telling Nest what it is for. Nest's decorators always end in (), even when nothing goes inside. Together they map findAll to GET /books, and Nest sends what the method returns as JSON with status 200. Nest never sends a request to a method that has no route decorator.

A module lists the classes that belong together. src/main.ts calls NestFactory.create(AppModule); AppModule imports TasksModule, which lists TasksController. On a laptop you would start it with npm run start; here Run does it.

In the starter, interface Task describes the fields of a task object, and Task[] means an array of them. private keeps a field inside its class. A type after a method’s parentheses describes its returned value. These annotations help TypeScript check your code; Nest’s decorators define the routes.

Challenge

Easy

Your first Nest server already holds three tasks, but no route returns them yet. Add the route that lists them.

Open src/tasks/tasks.controller.ts. The class TasksController holds the list in this.tasks. @Controller('tasks') above the class puts it in charge of paths under /tasks.
Where the comment is, add a method (call it findAll) and mark it with @Get(). It returns this.tasks. Nest sends what the method returns as JSON, with status 200.
Get comes from @nestjs/common, like Controller. Add it to the import on the first line.

Try it: press Run, then send GET /tasks. You get 200 and the three tasks:

[
  { "id": 1, "title": "Write the README", "done": true },
  { "id": 2, "title": "Fix the login bug", "done": false },
  { "id": 3, "title": "Plan the sprint", "done": false }
]

Then send GET /task, without the s. No route matches that path, so Nest responds with 404:

{ "message": "Cannot GET /task", "error": "Not Found", "statusCode": 404 }

Try it yourself

import { Controller } from '@nestjs/common';

interface Task {
    id: number;
    title: string;
    done: boolean;
}

@Controller('tasks')
export class TasksController {
    private tasks: Task[] = [
        { id: 1, title: 'Write the README', done: true },
        { id: 2, title: 'Fix the login bug', done: false },
        { id: 3, title: 'Plan the sprint', done: false },
    ];

    // Add a method here that answers GET /tasks with the list.
}