LESSONS.md

Lesson - Backend App

These are some notes taken from the second lesson of the OmnisTack 11th week.

Initiating the project

$ mkdir backend && cd backend
$ npm init -y
$ mkdir src
$ mv index.js src

Setting up hot reload:

$ npm install nodemon -D

Add a start script on package.json:

    ...
    "scripts": {
        "start": "nodemon src/index.js"
    },
    ...

Express: installing the web server and setting up some routes

$ npm install express
$ touch src/routes.js

Add your routes to the file you just created:

// src/routes.js
const express = require('express');
const routes = express.Router();

routes.get('/', (request, response) => {
    return response.send('Hello world');
});

module.exports = routes;

Import your routes into index.js:

// src/index.js
const express = require('express');
const routes = require('./routes');
const app = express();
app.use(express.json());
app.use(routes);
app.listen(3333)

Knex: setting up the database schema and connection

Knex Query Builder Docs.

Installation

$ npm install knex
$ npx init knex # this will create a knexfile.js config file at the root dir
$ mkdir src/database
$ mkdir src/database/migrations

Edit configs:

  // knexfile.js
  ...
  development: {
    client: 'sqlite3',
    connection: {
      filename: './src/database/db.sqlite3'
    },
    migrations: {
      directory: './src/database/migrations'
    },
    useNullAsDefault: true,
  },
  ...

Creating and executing Migrations:

$ npx knex # shows all commands available
$ npx knex migrate:make create_ongs
$ npx knex migrate:make create_incidents

Add to your create_ongs migration file:

// src/database/migrations/20200327000000_create_ongs.js
exports.up = function(knex) {
  return knex.schema.createTable('ongs', function(table) {
    table.string('id').primary();
    table.string('name').notNullable();
    table.string('email').notNullable();
    table.string('whatsapp').notNullable();
    table.string('city').notNullable();
    table.string('uf', 2).notNullable();
  })
};

exports.down = function(knex) {
  return knex.schema.dropTable('ongs');
};

Now, add the following to your create_incidents migration file:

// src/database/migrations/20200327000001_create_incidents.js
exports.up = function(knex) {
  return knex.schema.createTable('incidents', function(table) {
    table.increments();
    table.string('title').notNullable();
    table.string('description').notNullable();
    table.decimal('value').notNullable();
    table.string('ong_id').notNullable();

    table.foreign('ong_id').references('id').inTable('ongs');
  })
};

exports.down = function(knex) {
  return knex.schema.dropTable('incidents');
};

Run all migrations:

$ npx knex migrate:latest

If you need to undo something:

$ npx knex migrate:rollback

Finaly, create the connection object:

$ touch src/database/connection.js

// src/database/connection.js
const knex = require('knex');
const configuration = require('../../knexfile');

const connection = knex(configuration.development);
module.exports = connection;

Now you can import the db connection object and use it to perform database operations:

// src/routes.js
const connection = require('./database/connection');
...
routes.post('/ongs', async function(request, response){
  const {name, email, whatsapp, city, uf } = response.body;
  const id = 'someRandomBytes';

  await connection('ongs').insert({
    id, name, email, whatsapp, city, uf
  });

  return response.json({ id });
});
...

Tidying up

$ mkdir src/controllers
$ touch OngController.js

Move all the logic of the ong routes from the routes.js file to the recently created file OngController.js:

// src/controllers/OngController.js

const crypto = require('crypto');
const connection = require('../database/connection');

module.exports = {
  async index(request, response) {
    const ongs = await connection('ongs').select('*');

    return response.json(ongs);
  },

  async create(request, response) {
    const { name, email, whatsapp, city, uf } = request.body;
    const id = crypto.randomBytes(4).toString('HEX');

    await connection('ongs').insert({
      id, name, email, whatsapp, city, uf
    });

    return response.json({ id });
  }
}

CORS installation and setup

$ npm install cors

Add to index.js:

// src/index.js
...
const cors = require('cors');

const app = express();
app.use(cors());
...