Ruby on Rails

Contents

• 1 Installation
• 2 Development in Rails
  • 2.1 Models
  • 2.2 Views
  • 2.3 Controllers
  • 2.4 Routing
  • 2.5 RESTful Resources
  • 2.6 The Database
• 3 Publishing to Heroku
  • 3.1 Big Issue
• 4 Diving Deeper
  • 4.1 Other Goals
  • 4.2 Rails functions
    • 4.2.1 link_to
    • 4.2.2 form_with
    • 4.2.3 rake
    • 4.2.4 rack
    • 4.2.5 etc
  • 4.3 The Active Record
• 5 Further Reading
• 6 References

Installation

I just find it easier to do things in Linux. On a Windows machine, go on WSL. There is a Ruby installed but you probably want the most recent versions of Ruby and Rails. Get it from the RVM website. Next, you will need to

• Develop the app with Rails
• Publish it on Heroku

Development in Rails

Start from this guide. It is quite long but it introduces the MVC (Models, Controllers, Views) concept that Rails follows very well. There are other sources on youtube that follow the same steps as the guide.

So what is MVC?

Models

Let's start with the M. Models are objects to be stored in a database. Generating models goes like this

 rails generate model Name column1 column2:string column3:text etc

Where the data type for column1 is assumed to be a string if left blank. Notice how Name is singular and capitalized, that's a convention.

Models are located under /app/models/. If you want to see the schema of the database, check out /db/schema.rb.

Views

Generating views using HTML templates and embedded Ruby e.g. index.html.erb. These views correspond to controller actions (written controller#action).

Under views, you might see @variable syntax. These are variables have been defined previously in the controller.

While on the topic of syntax, Rails uses symbols to identify things. In particular, it uses them as keys when naming method parameters and looking things up in hashes. You can think of symbols as string literals that are magically made into constants.^[1]. For example

 redirect_to :action => "edit", :id => params[:id]

Views are located under /app/views/.

Controllers

Controllers define actions based on the HTTP requests that the user makes.

To generate a controller, type

 rails generate controller pages

The above generates a pages controller under app/controllers/pages.

Routing

This is where the action starts from the user's perspective. The user inputs an http request, the predefined routes (in /config/routes.rb) perform a controller action, possibly interacting with the database and generating a variable or more, then take the user to the view. For example, /config/routes.rb contains this

 get 'about' => 'pages#about'

to send the user to an "About" page. The controller has something like

class PagesController < ApplicationController
	def about
		@text='about me'
	end
end

And the view will have

<%= link_to 'index', root_path %>
<h1>About Me</h1>
<%= @text %>

RESTful Resources

A resource is the term used for a collection of similar objects, such as articles, people, or animals. You can create, read, update, and destroy items for a resource and these operations are referred to as CRUD operations. To define a REST resource, In config/routing.rb, under Rails.application.routes.draw do write

 :resources :quotes

The Database

The database configurations are stored in the file /config/database.yml. Assuming you are going to deploy the app on Heroku, which uses postgres, here are settings that are known to work

development:
  adapter: postgresql
  database: my_database_dev
  pool: 5
  timeout: 5000

test:
  adapter: postgresql
  database: my_database_test
  pool: 5
  timeout: 5000

production:
  adapter: postgresql
  username: myrails
  password: <%= ENV['MYAPP_DATABASE_PASSWORD'] %>

Publishing to Heroku

Heroku provides a guide ^[2] on publishing rails developed websites on their platform.

Big Issue

I read every article that had the words Heroku and Rails in it but couldn't get the database to connect. This is the command that finally did it^[3]

 heroku run rake db:migrate

Thanks codeacademy! Changing the environment to production might have been needed first^[4]. Here is how to check that

 $ rails console
 Rails.env.production?

There is a lot more to say about deployment. I will put some placeholders here.

Diving Deeper

Rails functions

link_to

form_with

rake

rack

etc

The Active Record

Further Reading

• Japanese source. Setting up database.yml for rails to work with heroku.

References

1. ↑ colon operator in Ruby
2. ↑ Heroku rails guide
3. ↑ codeacademy
4. ↑ Changing the environment to production