Setup

Before running, you should have the following installed on your machine:

• Ruby
• Rails
• Postgres
• MongoDB

Walkthrough

• Create the rails application: rails new rails-postgres-mongo

Setup Postgres connection for Rails application

• Change Gemfile from sqlite3 to pg so we will use our Postgres locally
• Change config/database.yml to:

default: &default
  adapter: postgresql
  pool: 5
  timeout: 5000

development:
  <<: *default
  database: rails_postgres_mongo_development

Create the model mapping for ActiveRecord

• Generate a new ActiveRecord model for User: rails g model User
• Change db/migrate/*_create_users.rb to:

class CreateUsers < ActiveRecord::Migration
  def change
    create_table :users do |t|
      t.string :name
      t.string :email
      t.timestamps null: false
    end
  end
end

Run migrations for Postgresql database

• Run rake db:create
• Run rake db:migrate

Test Postgres connection

• Run rails console:

> User.create!(name: “Chris”, email: “chris@compose.io”)

Create Mongo connection for Rails application

• Append to Gemfile: gem ‘mongoid’
• Run a Mongoid configuration installation script: rails g mongoid:config
• Replace config/application.rb line 7 with Bundler.require(:default, Rails.env)

Create Mongoid model files

• Run rails g model Status
• Change app/model/status.rb to:

class Status
  include Mongoid::Document
  include Mongoid::Timestamps

  field :user_id, type: Integer
  field :status, type: String
end

Create the relationships in the data model

• Define how user.rb will use status:

class User < ActiveRecord::Base

  def status
    Status.where(user_id: self.id).order_by({created_at: -1}).one
  end

  def status=(status)
    Status.create!(user_id: self.id, status: status)
  end

  def statuses
    Status.where(user_id: self.id).order_by({created_at: -1})
  end

end

• Define how status.rb will use user:

class Status
  include Mongoid::Document
  include Mongoid::Timestamps

  field :user_id, type: Integer
  field :status, type: String

  def user
    User.find(self.user_id)
  end
end

Start your application

rackup

open http://localhost:9292/

Setup a default route

Change config/routes.rb to:

Rails.application.routes.draw do
  root “users#index”
end

Create a users controller

rails g controller Users

Then, set the UsersController to:

class UsersController < ApplicationController
  def index
    @users = User
  end
end

Create view

<h1>Users</h1>

<ul>
  <%- @users.all.each do |user| %>
    <li><%= user.name %> - <%= user.status.status %></li>
  <%- end %>
</ul>

Add bootstrap stylesheets to the body

<!— Latest compiled and minified CSS —>
<link rel=“stylesheet” href=“https://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/css/bootstrap.min.css” integrity=“sha512-dTfge/zgoMYpP7QbHy4gWMEGsbsdZeCXz7irItjcC3sPUFtf0kuFbDz/ixG7ArTxmDjLXDmezHubeNikyKGVyQ==“ crossorigin=“anonymous”>

<!— Optional theme —>
<link rel=“stylesheet” href=“https://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/css/bootstrap-theme.min.css” integrity=“sha384-aUGj/X2zp5rLCbBxumKTCw2Z50WgIr1vs/PFN4praOTvYXWlVyh2UtNUU0KAUhAX” crossorigin=“anonymous”>

<!— Latest compiled and minified JavaScript —>
<script src=“https://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/js/bootstrap.min.js” integrity=“sha512-K1qjQ+NcF2TYO/eI3M6v8EiNYZfA95pQumfvcVrTHtwQVDG+aHRqLi/ETn2uB+1JqwYqVG3LIvdm9lj6imS/pQ==“ crossorigin=“anonymous”></script>

Let’s add a form to automatically add new statuses

Append this to your users#index form:

<%- form_for [:user, Status.new] do ||f| %>
  <div class=‘form-input’>
    <input type=‘text’ name=‘user’>
  </div>
  <div class=‘form-input’>
    <input type=‘text’ name=‘status’>
  </div>
<%- end %>

Add this your config/routes.rb to this:

  resources :users do
    resources :statuses
  end