02-user-registration.md

02. User registration

Configure database

I've removed all the comments and parameters (except for default profile) from config/database.yml. And added single url parameter to default profile.

default: &default
  adapter: postgresql
  encoding: unicode
  pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
  url: <%= ENV["DATABASE_URL"] %>

development:
  <<: *default
  database: <%= ENV.fetch("DB_NAME", "#{Rails.root.basename}_dev") %>

test:
  <<: *default
  database: <%= ENV.fetch("DB_NAME", "#{Rails.root.basename}_test") %>

production:
  <<: *default

Now we can configure connection to database by setting DATABASE_URL environment variable.

Setting up variables for development

We don't want to set environment variables manually every time we start development server or run tests. There is a gem to automate that - dotenv-rails. Add it to Gemfile in development & test section (see the first part of this tutorial). Create .env file and put DATABASE_URL=postgresql://127.0.0.1:5432/textie_development there.

Probably you need to add your username and password to this url, for example:

DATABASE_URL=postgresql://user:password@127.0.0.1:5432/textie_development

.env can contain sensetive information, so keep it private. Create .env.example with variables defintions and checkout it to your repository instead. Add public settings and settings for local development there.

# file: .env.example
DATABASE_URL=postgresql://localhost:5432/textie_development

Create user model

Generate models/user.rb and a migration file.

rails g model User email:citext:uniq full_name password_digest:string

citext stands for case-insensitive text. It is a special type in PostgreSQL that behaves as text but it is processed with LOWER function before comparisons.

To use it you need to enable the corresponding extension. In the generated migration file add enable_extension("citext") before create_table statement. I've also set null option to false and default value for full_name.

# file: db/migrate/yyyymmddhhmmss_create_users.rb
class CreateUsers < ActiveRecord::Migration[6.0]
  def change
    enable_extension("citext")

    create_table :users do |t|
      t.citext :email, null: false
      t.string :full_name, null: false, default: ""
      # ...

Add endpoint to create users

Add decent_exposure gem to Gemfile. It reduces boilerplate constructing entities from params and finds by id in controllers.

Create a controller

Generate a controller by running rails g controller api/v1/users.

In generated class add line expose :user. It makes a User instance available by calling method user. In the generated file define private user_params method and permit users' allowed attrbiutes in it.

Define create method. Here user is created from user_params method which is listed below. We try to save user here, and if it succeeds, we render show template (method user is also available there). Otherwise we send user's errors.

class Api::V1::UsersController < ApplicationController
  expose :user

  def create
    if user.save
      render :show, status: :created
    else
      render json: user.errors, status: :unprocessable_entity
    end
  end

  private

  def user_params
    params.require(:user).permit(:email, :full_name, :password)
  end
end

Create a view

Create file app/views/api/v1/users/show.json.jbuilder with following content. User is a method we exposed in controller. Here we create a JSON document with fields id, email and fullName and corresponding user attributes.

json.id user.id
json.email user.email
json.fullName user.full_name

Create a route

Here we add the default format for our /api/* route. So it's JSON by default when no Content-Type header provided.

# file: config/routes.rb
Rails.application.routes.draw do
  namespace :api, defaults: { format: 'json' } do
    namespace :v1 do
      resources :users, only: %i[create]
    end
  end
end

Test it

Run bundle exec rails server to start your application. In another terminal session run

curl -X POST localhost:3000/api/v1/users \
    -H "Content-Type: application/json" \
    -d '{"user":{"email":"user@example.com","password":"123456"}}'

You should see unformatted JSON output.

{"id":1,"email":"user@example.com","fullName":""}

Create an invalid user. You can omit email address/password, use invalid/the same email address.

curl -X POST localhost:3000/api/v1/users \
    -H "Content-Type: application/json" \
    -d '{"user":{"email":"user@example.com"}}'

You should see errors as a response.

{"password":["can't be blank"],"email":["has already been taken"]}