Fix me on Github

Join a growing community of over 1900 attendees and take your first step towards becoming a Rails Developer

Getting Started



  1. A working version of Rails 4.2. To determine if you’ve got a working version of Rails 4.2, type rails -v into your command prompt, or ask a mentor.
  2. Sublime Text. If you prefer another text editor like Vim, emacs, TextMate or Github’s Atom that’s fine too but these instructions will specifically mention Sublime.

Next steps

Open two command prompts.

To do this on Windows: Open the Command Prompt window by clicking the Start button, clicking All Programs, clicking Accessories, and then clicking Command Prompt.

To do this on Mac: Open Finder in the Dock. Select applications. Then choose utilities. Double click on Terminal.

You’ll use one of the command prompts to run your local Rails server and the other for entering all other commands.

Whenever you need to start or restart the rails server use the first command prompt and for all other command line work you can use the second command prompt.

Setting up our Rails app

rails new quick_blog -T

Entering this command into your command prompt will cause Rails to generate a new application and begin to install dependencies for your application. This process may take a few minutes, so you should let it continue. The -T is short for --skip-test-unit. We won’t be specifically covering testing just now, so we won’t need the test directory that Rails normally provides for you when generating a new project.

Once it has finished type:

cd quick_blog

Entering this command will change you into the folder where your application is stored. If you look at the contents of this folder you’ll see:

The default Rails application structure

This is the standard structure of a new Rails application. Once you learn this structure it makes working with Rails easier since everything is in a standard place.

Next we’ll run this fresh application to check that our Rails install is working properly. Type:

rails server

Open your web-browser and head to: http://localhost:3000 you should see something that looks like:

Rails default homepage

Now that you’ve created the Rails application you should open this folder using Sublime. Open up Sublime, then open the quick_blog folder that was just generated.

Creating basic functionality

Now we’re ready to get started building an actual blog. In your command prompt press Ctrl-c (hold down the Control key, and press c) to stop the Rails server, or use your second command prompt and navigate to your Rails application folder. Then you can use a Rails generator to build some code for you:

rails generate scaffold Post title:string body:text

Let’s break this command down: we’re asking rails to generate a scaffold (basic building blocks; think construction scaffolding) for a thing, or in Rails parlance a “resource”, we want to call a Post in our system. We want to give our Post two attributes: a title, which we want to be a string, and a body, which we want to be text.

A string is computer-speak for a short sequence of characters like "hello" or "Are you having fun, yet?", and can usually be as long as your average tweet. Blog titles tend to be short, so we’ll use a string for ours. text is like a string, but longer, so we’ll use it to have enough room to write as many paragraphs as we want in the body of our blog post.

After running your command, you’ll be presented with something that looks like:

Scaffolding posts

An important file that was generated was the migration file: db/migrate/20140528075017_create_posts.rb Note that, as this file name starts with a unique id including the date and time, yours will have a different set of numbers.

class CreatePosts < ActiveRecord::Migration
  def change
    create_table :posts do |t|
      t.string :title
      t.text :body


This file is Ruby code that Rails uses to manage how your data is stored in the database. You can see that this code is to create a table called Posts and to create two columns in this table, a title column and a body column. Finally we need to instruct Rails to apply this to our database. Type:

rake db:migrate

Once this command has run you can start up your Rails server again with rails server and then navigate to http://localhost:3000/posts to see the changes you’ve made to your application.

Empty posts list

From here you can play around with your application. Go ahead and create a new blog post.

Creating a new post

You’ll notice you can create new posts, edit or delete them. We’re going to add in some functionality to our new Rails app which enforces a rule that every post must have a title. Open app/models/post.rb in Sublime and add the line:

validates_presence_of :body, :title

To the code. Your post.rb file should look like:

class Post < ActiveRecord::Base
  validates_presence_of :body, :title

We can check that this works by editing our blog post, deleting the title and clicking Update Post. You’ll get an error informing you that you’ve just attempted to break the rule you just inserted:

Rails validation error

Making things prettier

Right now our show post page isn’t looking very good. We’ll open app/views/posts/show.html.erb in Sublime and make it look like the following:

 <p id="notice"><%= notice %></p>

 <h2><%= link_to_unless_current @post.title, @post %></h2>
 <%= simple_format @post.body %>

 <%= link_to 'Edit', edit_post_path(@post) %> |
 <%= link_to 'Back', posts_path %>

At this point you can refresh the show post page in your browser to see the changes you’ve made.

We’ll also want to make our blog listing prettier too, we’ll use a Rails partial (a partial is simply a reusuable block of HTML code. It’s part of a web page) to achieve this. We want our listing and the individual blog pages to look the same so first we’ll create a file: app/views/posts/_post.html.erb The underscore in front of the filename here tells Rails that this is a partial. We’ll take

 <h2><%= link_to_unless_current @post.title, @post %></h2>
 <%= simple_format @post.body %>

Out of app/views/posts/show.html.erb and put it in our _post.html.erb file. After that, change all three mentions of @post to be post instead. This means your _post.html.erb file will be:

 <h2><%= link_to_unless_current post.title, post %></h2>
 <%= simple_format post.body %>

In our show.html.erb file we want to insert the code to put our partial into our show view. Insert the code: <%= render partial: @post %> to make it look like:

 <p id="notice"><%= notice %></p>

 <%= render partial: @post %>

 <%= link_to 'Edit', edit_post_path(@post) %> |
 <%= link_to 'Back', posts_path %>

Save all these files and refresh the show posts page. This is to check that you haven’t broken anything with those changes.

Our index page still hasn’t changed, so we’re going to open the index.html.erb file up and remove the table in there and replace it with the partial again so we’re re-using that code:

 <h1>Listing posts</h1>

 <%= render partial: @posts %>

 <%= link_to 'New Post', new_post_path %>

Access control

One huge problem with our blog is that anyone can create, edit and delete blog posts. Let’s fix that. We’ll use HTTP Basic authenticate to put a password on actions we don’t want everyone accessing. Open app/controllers/posts_controller.rb and add before_filter :authenticate, except: [ :index, :show ] on line 2 just below the class declaration. At the bottom of your file put the following code:

  def authenticate
    authenticate_or_request_with_http_basic do |name, password|
      name == "admin" && password == "secret"

Overall your posts_controller.rb should have the following code at the top and the bottom of the file. Note that all the methods are excluded here for brevity.

class PostsController < ApplicationController
  before_filter :authenticate, except: [ :index, :show ]
  before_action :set_post, only: [:show, :edit, :update, :destroy]

  # all your actions go in here


  # there should be post_params and set_post methods in here.

  def authenticate
    authenticate_or_request_with_http_basic do |name, password|
      name == "admin" && password == "secret"

With that code in place you can try to add a new post and you’ll be prompted to enter a username and password.


Adding comments

Creating a database model and routing

No blog is complete without comments. Let’s add them in. On our command prompt, shut down your rails server by hitting Ctrl-C and then type in:

rails generate resource Comment post:references body:text

Then you’ll want to update your database here to reflect the schema change you’ve just made:

rake db:migrate

After this you’ll need to inform Rails that your Posts will potentially have many Comments. Open app/models/post.rb and add the line: has_many :comments somewhere inside the class. This should look like:

class Post < ActiveRecord::Base
  has_many :comments

  validates_presence_of :body, :title

The back-end for your comments is almost complete, we only need to configure the url that is used to create your comments. Since comments belong to a post, we’ll make the URL reflect this. Right now you can see all the configured URLs by typing rake routes in your command prompt. If you do this now you’ll get something like the following:

    comments GET    /comments(.:format)          comments#index
             POST   /comments(.:format)          comments#create
 new_comment GET    /comments/new(.:format)      comments#new
edit_comment GET    /comments/:id/edit(.:format) comments#edit
     comment GET    /comments/:id(.:format)      comments#show
             PUT    /comments/:id(.:format)      comments#update
             DELETE /comments/:id(.:format)      comments#destroy
       posts GET    /posts(.:format)             posts#index
             POST   /posts(.:format)             posts#create
    new_post GET    /posts/new(.:format)         posts#new
   edit_post GET    /posts/:id/edit(.:format)    posts#edit
        post GET    /posts/:id(.:format)         posts#show
             PUT    /posts/:id(.:format)         posts#update
             DELETE /posts/:id(.:format)         posts#destroy

Your URLs (or routes) are configured in all Rails applications in the file config/routes.rb, open it now and remove the line resources :comments. Re-run rake routes and you’ll notice that all the URLs for comments have disappeared. Update your routes.rb file to look like the following:

Rails.application.routes.draw do
  resources :posts do
    resources :comments, only: [:create]

  # root 'welcome#index'

Because comments will be visible from the show Post page along with the form for creating them, we don’t need to have URLs for displaying comment listings, or individual comments. When you rerun rake routes you’ll now see the following line:

post_comments POST   /posts/:post_id/comments(.:format) comments#create

Before we’re finished with the backend for our commenting system we need to write the action that will create our comments. For more information on actions please read the Rails Guide on ActionController.

Open app/controllers/comments_controller.rb and make your code look like the following:

class CommentsController < ApplicationController
  def create
    @post = Post.find(params[:post_id])
    @comment = @post.comments.create!(comment_params)
    redirect_to @post


  def comment_params

The big difference here from Rails 3 to Rails 4 is that we use a method called comment_params to only choose the parameters from the form that we want to save to the model. You can read more about this at:

Putting comments into your HTML view

You’ve created the database model for your comments, migrated your database, informed Rails of the relationship between comments and posts, configured a URL that lets you create your comments and created the controller action that will create the comments. Now you need to display any comments that have been submitted for a post, and allow users to submit comments. Open app/views/posts/show.html.erb and make it look like:

 <p id="notice"><%= notice %></p>

 <%= render partial: @post %>

 <%= link_to 'Edit', edit_post_path(@post) %> |
 <%= link_to 'Back', posts_path %>

 <div id="comments">
  <%= render partial: @post.comments %>

You’ll now need to create a file called app/views/comments/_comment.html.erb with the following contents:

<%= div_for comment do %>
      Posted <%= time_ago_in_words(comment.created_at) %> ago
    <%= comment.body %>
<% end %>

Back in app/views/posts/show.html.erb you need to add in the form for submitting a comment so add the following code to the bottom of that file.

<%= form_for [@post,] do |f| %>
    <%= f.label :body, "New comment" %><br/>
    <%= f.text_area :body %>
  <p><%= f.submit "Add comment" %></p>
<% end %>

Comments are now working (if they aren’t make sure you restart your rails server), so go ahead and browse to your post and add a new comment.

Publishing your Blog on the internet

Heroku is a fantastically simple service that can be used to host Ruby on Rails applications. You’ll be able to host your blog on Heroku on their free-tier, but first you’ll need a Heroku account. Head to, click Sign Up and create an account. The starter documentation for Heroku is available at: Once you’ve got an account you’ll need to download the toolbelt from and set it up on your computer.

Make the application work on Heroku

Up until this point we’ve been using SQLite as our database, but unfortunately Heroku doesn’t support the use of SQLite. So we’re going to be running Postgres instead.

We need to do some other things to make our application work on Heroku (it has to follow the “Twelve-Factor” rules – don’t worry about the details).

These changes are easy to make. You’ll need to open the Gemfile and make your Gemfile look like:

source ''

gem 'rails', '~> 4.2.0'

gem 'sqlite3', group: [:development, :test]
gem 'pg', group: :production

gem 'sass-rails', '~> 5.0'
gem 'uglifier', '>= 1.3.0'
gem 'coffee-rails', '~> 4.1.0'

gem 'jquery-rails'
gem 'turbolinks'
gem 'jbuilder', '~> 2.0'
gem 'sdoc', '~> 0.4.0',          group: :doc
gem 'spring',        group: :development
gem 'rails_12factor', group: :production

After this, run the command bundle install --without=production on your command line.

Regarding version control

Heroku also requires that every application is placed under version control before it is deployed. Simply run the following commands on the command prompt to make sure your application is properly controlled:

git init
git add .
git commit -m "initial blog commit"

Deploying your application

In the same command prompt you should be ready to deploy your application. First we create our Heroku application:

heroku create

Now we push our application to Heroku:

git push heroku master

Finally we set up our database:

heroku run:detached rake db:setup

This setup of the database should only need to take place the first time you deploy to heroku. Afterwards you may need to run heroku run rake db:migrate instead. The detached option runs the command in the background. It is there only to ensure the process will go through, even on faulty Internet connection. You can use heroku logs to view the output of the command.

To check that your blog has been deployed properly, browse to the URL that Heroku has given you, remembering to append “/posts” to the end of the URL. e.g.

Note that you can also use the heroku open command to get to the root URL (and then append the “/posts” to that URL)

Welcome to Ruby on Rails. If you’re this far along you should definitely head on over to Part 2 which goes more in depth with Rails and begins to add more features to the blogging engine.