poll-api

This repository contains a complete RESTful Rails-api along with a clean documentation which walks developers through all construction steps. If you wish to start with ruby on rails, this repository is a great resource for you.

AngularJS Front-End Repository

Ruby on Rails Cheat Sheet

Definitions

• Homebrew is for downloading and installing open source apps on mac. It is an open source package manager.
• RVM is a version manager for ruby which lets you have projects which work with different versions of ruby.
• RubyGems is a package manager for installing plugins and libraries for use with ruby rails.
• A Gem is a ruby code packed for easy distribution. RubyGems.org is a public gem repository.
• Rails itself is a gem.
• Bundler is a gem that helps your rails app to load the right ruby gems.
• Rake is a gem which will make tasks.

Setup

• Install homebrew
• Install rvm: https://rvm.io/rvm/install#1-download-and-run-the-rvm-installation-script
• Find out the latest versions of rails and ruby: http://ruby-lang.org, http://rubyonrails.org/

$ rvm get head
$ rvm list known
$ rvm install 2.3.6 (or the version you want)
$ rvm list
$ rvm --default use 2.3.6 (or the version you want)
$ gem install bundler
$ gem install rails --no-document (for latest or specify a version: -v 5.0.1)

• You could have several rubies installed. For each, there could be several gemsets only one of which is active at a time.

$ gem list (gives list of gems in your active gemset)
$ gem update --system (update all gems)
$ rvm gemset list (list of gemsets for current ruby version)

• Install nvm using homebrew and then follow instructions outputed to activate it
• nvm ls-remote find the latest LTS version in the list and do nvm install 10.16.3
• To switch node version: nvm use 10.15.0 and to make a version default do nvm alias default 10.15.0

Create Project

$ cd /your/desider/path
$ rails new <name> (--api)?

Install Gems

Whenever you need to install a gem, add to Gemfile:

gem 'name'

Then do:

$ bundle install

If at some point some command did not work for your project you need to put bundle exec at front of it so that the command is executed in the context of the specific bundle of gems your project has.

Database Setup

MySQL

$ brew install mysql

At the end it will give you a command that make mysql launch at startup. You can always manually do:

$ brew services stop/start mysql

Set password for user root:

$ mysqladmin -u root password

Add -p if root already has a password and you want to change it. Login to MySql, create database and a user:

$ mysql -u <user> -p
> show databases;
> create database my_db;
> grant all privileges on my_db.* to 'my_user'@'localhost' identified by 'my_pass'

Install mysql2 gem and configure config/database.yml

MongoDB

$ brew install mongodb

If mongodb is going to be accessed from outside of server, you need to create a user that has appropriate access on that specific db name Set password for user root:

$ mongo
> show dbs
> use admin
> db.createUser({
  user: "root",
  pwd: "<password>",
  roles: [{ role: "dbAdminAnyDatabase", db: "admin" }]
})

Create a user for a specific db name and make that user owner of the db

> use my_db
> db.createUser({
  user: "my_user",
  pwd: "<password>",
  roles: ["dbOwner"]
})

On server, mongodb is usually protected by authentication. If you have password for root:

mongo --port 27017 -u "root" -p "<password>" --authenticationDatabase "admin"

If you don't have password of root you need to comment out security and authorization in /etc/mongod.conf, restart the mongodb service and do the above steps.

If you are making a new rails app add --skip-active-record. If you already have an app, delete any lines starting with config.active_record from config/environments/development and config/environments/production then open config/application.rb and replace require 'rails/all' with:

require "rails"
require "active_model/railtie"
require "active_job/railtie"
require "action_controller/railtie"
require "action_mailer/railtie"
require "action_view/railtie"
require "action_cable/engine"
require "sprockets/railtie"
require "rails/test_unit/railtie"

Install gem mongoid Then do:

$ rails g mongoid:config

Configure config/mongoid.yml accordingly. Put the following code in ~/.irbrc:

if Object.const_defined?('Rails') && Object.const_defined?('Mongoid')
	Mongoid.load!("#{Rails.root}/config/mongoid.yml")
end

Postgresql

$ brew install postgresql

Create rails app with --database=postgresql or install gem pg and configure config/database.yml

$ rails db:create

For installing postgres on ubuntu in production:

$ sudo apt-get install libpq-dev
$ sudo apt-get install postgresql postgresql-contrib

Postgresql super user postgres is used for administation and database postgres is used for users and database data. To reset the password of postgres role or user:

$ sudo vim /etc/postgresql/<VERSION>/main/pg_hba.conf

Change peer to trust for local all postgres and local all all then do a sudo service postgresql restart Now connect to psql client with postgres user:

[Command shell with postgres user] 
$ psql -U postgres

[Change super user password]
ALTER USER postgres with password 'new-password';

[OR Create super user no password]
postgres=# CREATE ROLE postgres WITH SUPERUSER CREATEDB CREATEROLE LOGIN;

[Make a special user and db]
postgres=# CREATE ROLE my_user WITH LOGIN PASSWORD 'password';
postgres=# ALTER ROLE my_user CREATEDB;
postgres=# CREATE DATABASE my_db;
postgres=# GRANT ALL PRIVILEGES ON DATABASE my_db TO my_user;

[Bonuses]
postgres=# \du
postgres=# \list
postgres=# \connect my_db
postgres=# \dt
postgres=# \q

[Syntax]
$ psql db_namee -U user 

[Main DB with no user] 
$ psql postgres

After this, revert the changes in pg_hba.conf file from trust to md5 and restart postgresql.

Importing dumps:

$ psql db_name < dump.sql

Rails Commands

• Run server

$ rails s (production)?

• Run console

$ rails c (production)?

• Help for generating stuff

$ rails g 

Views

• Insert ruby code in views:

<% code %>

• Print value of an expression:

 <%= expression %>

• Drop variables in strings:

"the beginning ... #{var} ... the end"

• Generating links, images, forms, etc. using rails helpers:

<%= image_tag('logo.png') %>
<%= link_to(name, target) %>

target could be rails hash:

{controller: 'x', action: 'y', some_param: 't', …}

Layouts

You can create as much html.erb layouts as you wish in views/layouts. Then put <%= yield %> inside them to specify where you want html fragments to be rendered. In the controller class you need to specify layout 'name without html.erb>'. The default layout is called application.

Partials

You can exclude similar html fragments from full templates and put them in a Partial file. Partials have _ at the beginning of their name. The below code is used to yield a partial within a full template:

<%= render partial: 'name_or_path', locals: {key: value, …}) %>

Helpers

Rails provide a very strong set of text, number, date and more helpers. Just search for whatever you want to do first, it is likely that a function already exists for that. You can also create custom helper functions to use in the views. There are also sanitize helpers. Consider using them. They are absolutely necessary.

Assets

Put all asset files in app/assets for rails to be able to perform optimization processes for production environment. In development environment, rails directly uses asset files in app/assets. In production however, it will optimize all asset files and put them in public/assets. Different kind of assets are kept in different folders under app/assets. In all of them there is a manifest file called application. The comments at the beginning of these files are the manifest and are used as input to the optimization process. If you wish to process asset files of a particular kind in a certain order, you must explicitly define this order. To do that, before //= require_tree . add //= require <asset_name>

Controllers

Rendering Templates

By default, each controller action renders a template in views/<controller_name>/<action_name>.html.erb.

To overwrite this default behavior, you can put render command in controller actions:

render template: 'path/to/the/view/template'

The template being rendered has access to all instance variables of the action which are those with @ at the beginning.

Redirecting

redirect_to controller: :x, action: :y

or

redirect_to 'google.com'

Accessing Request Parameters

Request parameters can be accessed using:

params[:key]

Rails 4 has a very strong way of passing parameters when instantiating model objects in controllers called Mass Assignment. You can create a safe parameter hash and pass it to model new or create methods using the require and permit methods:

params.require(:user).permit(:username, :email, :password)

Migrations

Ignore if you are using mongoid

$ rails generate migration name_for_migration

In each migration ruby class, put an up and a down method. These methods must be in the mirror order of each other.

In up method u can do:

create_table :cards do |t| 
  t.string :name [, options]?	
  t.integer :student_id
  t.timestamps
end
drop_table :cards
add_column :cards, :name, :string
remove_column :cards, :name
add_index :cards, :student_id
add_index :cards, [:student_id, :course_id]

Available types include:

binary, boolean, date, datetime, decimal, float, integer, string, text, time

Available options:

limit: size
default: value
null: true/false
precision: number (for decimal type only)
scale: number (for decimal type only)

Migration commands:

$ rails db:migrate:status
$ rails db:migrate
$ rails db:migrate VERSION=0
$ rails db:rollback [STEP=n]?
$ rails db:migrate(:up/down/redo)? VERSION=number

It is a good practice to add index on all foreign key columns and those columns which are used frequently to look up for a row of data.

If you have a typo in your migration code it will cause the migration run to abort and you will get stuck in a state where you can not either go up or down. In such states just comment those executed lines of the broken method and try running the migration method again.

Models

One-to-one Association

Complete association reference

MySQL or Postgresql

class Student < ApplicationRecord 
  has_one :card
end
class Card < ApplicationRecord
  belongs_to :student
end

You also need to add foreign key to the belongs_to side in the migration file:

create_table :cards do |t| 
  t.integer :student_id
end

When you set student.card or card.student, rails automatically saves the relationship in the database. Also if you set any of these to nil you will break the relationship.

MongoDB

class Student
  include  Mongoid::Document
  has_one :card 
  # OR
  embeds_one :card
end
class Card
  include  Mongoid::Document
  belongs_to :student
  # OR
  embedded_in :student
end

One-to-many Association

MySQL or Postgresql

class Course < ApplicationRecord 
  has_many :projects
end
class Project < ApplicationRecord
  belongs_to :course
end

You also need to add foreign key to the belongs_to side in the migration file:

create_table :projects do |t| 
  t.integer :course_id
end

MongoDB

class Course
  include  Mongoid::Document
  has_many :projects 
  # OR
  embeds_many :projects
end
class Project
  include  Mongoid::Document
  belongs_to :course
  # OR
  embedded_in :course
end

Then you can do things like:

course.projects
course.projects << p
course.projects = [p1, p2, p3]
course.projects.destroy(p1) # destroys completely 
course.projects.delete(p1) # deletes from the list of projects
course.projects.clear
course.projects.empty?
course.projects.size

If you perform any modification on course.projects, rails will instantly sync the database accordingly.

Many-to-many Association

MySQL or Postgresql

class Student < ApplicationRecord 
  has_and_belongs_to_many :courses
end
class Course < ApplicationRecord
  has_and_belongs_to_many :students
end

You have to generate a migration to create join table for this relationship. Rails naming convention for the name of join table is:

first_table + _ + second_table

(in alphabetical order)

The migration file should look like this:

def up
  create_table :courses_students, :id => false do |t|
    t.integer :student_id
    t.integer :course_id
  end 
  add_index :courses_students, [:student_id, :course_id]
end

def down
  drop_table :courses_students
end

MongoDB

class Student
  include  Mongoid::Document
  has_and_belongs_to_many :courses
end
class Course
  include  Mongoid::Document
  has_and_belongs_to_many :students
end

If you change the name of the relationship from its default name, you would have to configure the relationship in order for it to work as it should:

join_table: :table_name
class_name: 'ActualClassNameInCaseYouChangeTheRelationshipKey'
foreign_key: :name_of_column_used_as_foreign_key

Again, If you perform any modification on objects in either side of such relationship, rails will instantly sync the database accordingly.

Inheritance

Two main types of class inheritance:

• Single Table Inheritance
• Class Table Inheritance (https://github.com/mvdamme/dbview_cti)

Create, Update, and Delete

u = User.new
u.assign_attributes(hash) # Update without saving
u.update_attributes(hash) # Update and save
u.update_attributes!(hash) # Update and raise errors
u = User.new(hash) # initialize object
u.new_record? # has it been saved in the database?
u.save # save and return true false
u.save! # save and raise error
u = User.create(hash) # new and save 
u = User.create!(hash) # new and save and raise error
u.destroy

Fetching Objects

u = User.find_by(hash)
u = User.find_or_create_by(hash) # try to find, create if not found
User.all
User.first
User.last
User.where(hash)
User.where([“column_1 = ? and column_2 > ?”, a, b])

where, order, offset, and limit are query methods available to ActiveRecord class.

Named Scopes are to make use of the above four methods but in a nicer way. For that, just add scopes to a Model:

scope :name, -> (params) { where(hash) }

and then we use it like:

Model.scope_name

Validation

List of validation functions:

validates_presence_of 
# options -> :message

validates_length_of
# options -> :is, :minimum, :maximum, :within, :in, :wrong_length, :too_short, :too_long

validates_numericality_of 
# options -> :equal_to, :greater_than, :less_than, :greater_than_or_equal_to, :less_than_or_equal_to, :odd, :even, :only_integer, :message

validates_inclusion_of
# options -> :in, :message

validates_exclusion_of
# options -> :in, :message

validates_format_of
# options -> :with, :message

validates_uniqueness_of
# options -> :case_sensitive, :scope, :message

validates_acceptance_of
# options -> :accept, :message

validates_confirmation_of
# options -> :message

Global Options we can use on almost all of the above:

:allow_blank
:allow_nil
on: :create/:update/:save(default)
if: :method_name 
# a boolean returner function, indicating whether or not the object should be validated

There is another way to write validations called Sexy Validation:

validates 
  :attribute_to_check,
  :presence => {}, # or a boolean
  :numericality => {}, # or a boolean
  :length => {},
  :format => {},
  :inclusion => {},
  :exclusion => {},
  :acceptance => {},
  :uniqueness => {},
  :confirmation => {}

Call .valid? on objects to check their validity. Call .errors on objects to see its errors.

You can also add your own custom validation methods to the model:

def :name_of_validation 
	# check validation criteria
	# finally do:
	errors.add(:attribute or :base, "msg") 
end

And declare this validation on the Model:

validate :method_name 
# you can also add :on or :if options here

Callbacks

There are:

before_create
before_save
before_validation
before_commit
before_update

after_create
after_save
after_validation
after_commit
after_update

If you want to see if any attribute has changed in after callbacks, use self.saved_change_to_attribute?(:title) and attribute_before_last_save(attr_name) Read here

Cookies and Sessions

To set a cookies and session variables:

cookies[:key] = val
session[:key] = val
cookies[:username] = {
  value: val,
  expires: 1.week.from_now
}

Session data can be stored in file, database, or we can use cookies to store them. Since we are sending information to the user's local machine we need a mechanism to check whether or not they are changed by anyone other than us. Rails use the secret key stored in config/initializers/secret_token.rb to validate the integrity of signed cookies.

$ rake secret will produce new key for you which you can replace the old one with.

The configuration to make rails use cookies for storing sessions is stored in config/initializers/session_store.rb

RESTful Routes

To see all routes of your app, do:

$ rails routes 

Below is the standard list of RESTful routes:

| URL                  | HTTP Method | Controller Action | Description                        |
|----------------------|-------------|-------------------|------------------------------------|
| /subjects            | GET         | index             | Show all items                     |
| /subjects/new        | GET         | new               | Show new form                      |
| /subjects            | POST        | create            | Create an item                     |
| /subjects/:id        | GET         | show              | Show item with :id                 |
| /subjects/:id/edit   | GET         | edit              | Show edit form for item with :id   |
| /subjects/:id        | PATCH       | update            | Update item with :id               |
| /subjects/:id/delete | GET         | delete            | Show delete form for item with :id |
| /subjects/:id        | DELETE      | destroy           | Delete item with :id               |

You can find routing configuration file in: config/routes.rb

Building a RESTful Rails API

First, install this gem following instruction in its repo.

Then you need to add routes for your RESTful API:

namespace :api, :defaults => {:format => :json} do
  resources :users, :only => [:create]
end

Then in controller actions you render json responses:

render json: obj, status: 200
# OR
render nothing: true, status: 200

Authentication

MySQL and Postgresql

• Install bcrypt gem.
• Add a column named password_digest on your users table.
• Then simply add has_secure_password in the User model. What it does, is it adds a virtual attribute named password to that model. It also adds validation to check if password and password_confirmation are present and then whether or not they match.
• Set plain password on a new user object and call save. It will encrypt this password and save it in password_digest.
• Check if user's given password is correct:

u = User.last
u.authenticate('give password') # returns false or user

Mongoid

• Install bcrypt gem
• Add the following code to your User model.

class User
  include Mongoid::Document
  include BCrypt
  field :password_hash, type: String

  def password
    if !password_hash.nil?
      @password ||= Password.new(password_hash)
    end
  end

  def password=(new_password)
    if !new_password.blank?
      @password = Password.create(new_password)
    end
    self.password_hash = @password
  end
end

• Check if user's give password is correct:

u = User.last
u.password == 'given password'

After Password is Confirmed

Put the username of the logged in user in session

If your application is only a rails api, you need to generate a Json Web Token instead of cookie session and send it back to user. To create this token, follow the instructions here.

To check if user has logged in when they request for an action, first, add this method to ApplicationController:

private

def confirm_logged_in 
  if <token is valid>
    return true
  else 
    render nothing: true, status: 401
    return false
  end
end

Now you have to add this line to all controllers to check if the user has logged in before an actions is actually run:

before_action :confirm_logged_in, except: [:action_1]
# OR
before_action :confirm_logged_in, only: [:action_3]
# OR a combination of both :only and :except

Deploy on Ubuntu VPS

• Make an ubuntu user to use for deployment

$ sudo adduser deploy
$ sudo adduser deploy sudo
$ su deploy

• Install RVM

$ sudo apt-get install libgdbm-dev libncurses5-dev automake libtool bison libffi-dev
$ gpg --keyserver hkp://keys.gnupg.net --recv-keys 409B6B1796C275462A1703113804BB82D39DC0E3 7D2BAF1CF37B13E2069D6956105BD0E739499BDB
$ curl -sSL https://get.rvm.io | bash -s stable
$ source ~/.rvm/scripts/rvm
$ rvm install 2.3.6
$ rvm use 2.3.6 --default

• Install ca-certificates, nginx, curl, git

$ sudo apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 561F9B9CAC40B2F7
$ sudo apt-get install -y apt-transport-https ca-certificates curl git-core nginx -y

• Now Nginx is a service

$ sudo service nginx start|stop|restart|status

• Install rails and bundler

$ gem install bundler
$ gem install rails -v 5.x.x

• Make a SSH key

$ ssh-keygen -t rsa
Enter This name: /home/deploy/.ssh/#{appname}_rsa

• Print this key, and add it to your repo keys

$ cat /home/deploy/.ssh/#{appname}_rsa.pub

• Open ~/.ssh/config and put the following line

IdentityFile ~/.ssh/#{appname}_rsa

• Check if your access is set:

$ ssh -T [email protected]
or
$ ssh -T [email protected]

• Add to your gem file

group :development do
  gem 'capistrano',         require: false
  gem 'capistrano-rvm',     require: false
  gem 'capistrano-rails',   require: false
  gem 'capistrano-bundler', require: false
  gem 'capistrano3-puma',   require: false
end

• Bundle

$ bundle install

• create capistrano files

cap install

• Edit Capfile and paste

require 'capistrano/setup'
require 'capistrano/deploy'
require "capistrano/scm/git"
install_plugin Capistrano::SCM::Git

require 'capistrano/rails'
require 'capistrano/bundler'
require 'capistrano/rvm'
require 'capistrano/puma'
install_plugin Capistrano::Puma

Dir.glob('lib/capistrano/tasks/*.rake').each { |r| import r }

• Paste the following in config/deploy.rb and edit server_path, repo_url, application_name

# Change these
server '200.122.181.42', port: 22, roles: [:web, :app, :db], primary: true

set :repo_url,        '[email protected]:mefeghhi/poll-api.git'
set :application,     'poll-api'
set :user,            'deploy'
set :puma_threads,    [4, 16]
set :puma_workers,    0

# Don't change these unless you know what you're doing
set :pty,             true
set :use_sudo,        false
set :stage,           :production
set :deploy_via,      :remote_cache
set :deploy_to,       "/home/#{fetch(:user)}/apps/#{fetch(:application)}"
set :puma_bind,       "unix://#{shared_path}/tmp/sockets/#{fetch(:application)}-puma.sock"
set :puma_state,      "#{shared_path}/tmp/pids/puma.state"
set :puma_pid,        "#{shared_path}/tmp/pids/puma.pid"
set :puma_access_log, "#{release_path}/log/puma.error.log"
set :puma_error_log,  "#{release_path}/log/puma.access.log"
set :ssh_options,     { forward_agent: true, user: fetch(:user), keys: %w(~/.ssh/id_rsa.pub) }
set :puma_preload_app, true
set :puma_worker_timeout, nil
set :puma_init_active_record, true  # Change to false when not using ActiveRecord

## Defaults:
# set :scm,           :git
# set :branch,        :master
# set :format,        :pretty
# set :log_level,     :debug
# set :keep_releases, 5

## Linked Files & Directories (Default None):
# set :linked_files, %w{config/database.yml}
# set :linked_dirs,  %w{bin log tmp/pids tmp/cache tmp/sockets vendor/bundle public/system}

namespace :puma do
  desc 'Create Directories for Puma Pids and Socket'
  task :make_dirs do
    on roles(:app) do
      execute "mkdir #{shared_path}/tmp/sockets -p"
      execute "mkdir #{shared_path}/tmp/pids -p"
    end
  end

  before :start, :make_dirs
end

namespace :deploy do
  desc "Make sure local git is in sync with remote."
  task :check_revision do
    on roles(:app) do
      unless `git rev-parse HEAD` == `git rev-parse origin/master`
        puts "WARNING: HEAD is not the same as origin/master"
        puts "Run `git push` to sync changes."
        exit
      end
    end
  end

  desc 'Initial Deploy'
  task :initial do
    on roles(:app) do
      before 'deploy:restart', 'puma:start'
      invoke 'deploy'
    end
  end

  before :starting,     :check_revision
  after  :finishing,    :compile_assets
  after  :finishing,    :cleanup
end

# ps aux | grep puma    # Get puma pid
# kill -s SIGUSR2 pid   # Restart puma
# kill -s SIGTERM pid   # Stop puma

• Edit your firewall to let incoming connection to port 22 (80 and 443)
• Create file config/nginx.conf and paste the following and edit appname

upstream puma {
  server unix:///home/deploy/apps/#{appname}/shared/tmp/sockets/#{appname}-puma.sock;
}

server {
  listen 80 default_server deferred;
  # server_name example.com;

  root /home/deploy/apps/#{appname}/current/public;
  access_log /home/deploy/apps/#{appname}/current/log/nginx.access.log;
  error_log /home/deploy/apps/#{appname}/current/log/nginx.error.log info;

  location ^~ /assets/ {
    gzip_static on;
    expires max;
    add_header Cache-Control public;
  }

  try_files $uri/index.html $uri @puma;
  location @puma {
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    proxy_set_header Host $http_host;
    proxy_redirect off;

    proxy_pass http://puma;
  }

  error_page 500 502 503 504 /500.html;
  client_max_body_size 10M;
  keepalive_timeout 10;
}

• Issue deploy command from development machine

$ cap production deploy:initial

• Create a shortcut or (symbolic link) to config/nginx.conf in sites-enabled

$ sudo rm /etc/nginx/sites-enabled/default
$ sudo ln -nfs "/home/deploy/apps/#{appname}/current/config/nginx.conf" "/etc/nginx/sites-enabled/#{appname}"

• Restart Nginx

$ sudo service nginx restart
OR 
$ sudo systemctl restart nginx.service
$ sudo journalctl -u nginx.service -f (logging live a service with name)

You should now be able to point your web browser to your server IP and see your Rails app in action!

• If you make change to config/nginx.conf, commit, issue a deploy command: $ cap production deploy and restart nginx on the server: sudo service nginx restart
• You might need to add environment variables in production server to read db password or secret_key_base. To do so, add variables like below to /etc/environment and reboot the server:

VAR_NAME="value"

Domain parking

read:

• How to point your domain to DigitalOcean servers

• How to point your DigitalOcean server to your domain

Setting up HTTPS

Read steps for setting up lets encrypt

Rspec, Capybara, FactoryBot

• RSpec 1
• RSpec 2
• RSpec 3
• Best Practices
• Capybara Docs Capybara Cheatsheet
• FactoryBot