Creating a Complete CRUD API Part One

Now you will combine several Nest.js concepts and start building a small CRUD API.

CRUD stands for:

• Create;
• Read;
• Update;
• Delete.

In this part, you will set up a simple users API with routes for creating users and getting all users.

Start with the service:

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

@Injectable()
export class UsersService {
  private users = [
    { id: 1, name: 'Alice', age: 30 },
    { id: 2, name: 'Bob', age: 25 },
  ];

  getAllUsers() {
    return this.users;
  }

  createUser(user: { name: string; age: number }) {
    const newUser = {
      id: this.users.length + 1,
      ...user,
    };

    this.users.push(newUser);
    return newUser;
  }
}

Here is what is happening:

• users: stores the current list of users;
• getAllUsers(): returns all users;
• createUser(): creates a new user and adds it to the array.

Now update the controller:

import { Controller, Get, Post, Body } from '@nestjs/common';
import { UsersService } from './users.service';

@Controller('users')
export class UsersController {
  constructor(private usersService: UsersService) {}

  @Get()
  getUsers() {
    return this.usersService.getAllUsers();
  }

  @Post()
  createUser(@Body() body: { name: string; age: number }) {
    return this.usersService.createUser(body);
  }
}

Here is what is happening:

• @Get(): returns all users;
• @Post(): creates a new user;
• @Body(): gets data from the request body;
• The controller passes the work to the service.

With this setup, your API can already:

• Return all users;
• Create a new user.

This is the first half of a CRUD API.