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An Introduction to
Ruby on Rails
1

An Introduction to Ruby and Rails
Outline
?What is Ruby?
?What is Rails?
?Rails overview.
?Sample RoR application and also with Spree
gem.
2

What is Ruby?
? Ruby is a pure object oriented programming language. It was
created on February 24, 1993 by Yukihiro Matsumoto of Japan.
Ruby is a general-purpose, interpreted programming language.
3

What is Rails?
? Rails is a web application development framework written in
the Ruby language. It is designed to make programming web
applications easier by making assumptions about what every
developer needs to get started.
? Open Source (MIT license)
? Based on a existing application (Basecamp)
? Provides common needs:
- Routing, sessions
- Database storage
- Business logic
- Generate HTML/XML/CSS/Ajax
? It allows you to write less code while accomplishing more than
many other languages and frameworks.
4

Rails Advantages
? Convention over configuration
? Don��t Repeat Yourself
? Object Relational Mapping
? Model View Controller
? Reuse of code
5

Convention over Configuration
? Table and foreign key naming
- Tables are multiples (users, orders, ��)
- Foreign key naming: user_id
? Default locations
- MVC, Test, Languages, Plugins
? Naming
- Class names: CamelCase
- Files: lowercase_underscored.rb
6

Don��t repeat yourself
? Everything is defined in a single, unambiguous place
? Easier to find code
- Only need to look once
- Can stop looking when found
- Well defined places for most items
? Much easier to maintain code
- Faster to change
- Less inconsistency bugs
7

8An Introduction to Ruby and Rails
MVC
? Model
- Object relationships
(users, orders)
? Controller
- Business logic (perform
a payment)
? View
- Visual representation
(generate HTML/XML)
8

Object Relational Mapping
- Easily stored and retrieved
from a database without writing
SQL statements directly
- Use with less overall database
access code
9

Re-use of code
? Gems and plugins, more then 1300
- For authentication, pagination, testing, ��
? Git allows easy forking and merging
10

Rails Disadvantages
? Rails is inefficient
? Rails is hard to desploy
11

Rails is inefficient
? Rails uses a lot of memory, up to 150MB per instance
? Requires more application servers
? Where are your development constrains?
12

Rails is hard to deploy
? Harder than PHP, better with Passenger
? Lots of moving parts
- Rails, apps, gems, plugins
- Application server, webserver
? Deployment via scripts
- Via the Capistrano tool
- Easy to break something
? Deployment to multiple servers
13

Quick Rails Demo:
? $ rails new RoRApp
$ cd RoRApp
(Use an Aptana studio IDE)
? We have 3 environments( in config/database.yml)
1.Development
2.Test
3.Production
14

? If we want to configure the database as mysql2(default database is
sqllite), open the file config/database.yml and modify the database
name and options.
development:
adapter: mysql2
encoding: utf8
database: db/development/dev
username: root
Password: '123456'
? And also we need to add myspl2 gem in Gemfile as
gem 'mysql2'
Configuring the Database:
15

Now we need to bundle update which installs the mysql2
gem for our application.
$ bundle update
Create a Database :
? Now we have our database is configured, it��s time to have Rails
create an empty database. We can do this by running a rake
command:
$ rake db:create
16

1.rails s (or) (default port is 3000)
2.rails server (or)
3.rails s -p 4000
? Verify whether the rails app is working properly or not by browsing
http://localhost:3000
? Here the default page is rendering from public/index.html
17

? If we want to display a user defined text or anything in our home
page, we need to create a controller and a view
$ rails generate controller home index
Rails will create several files, including
app/views/home/index.html.erb and
app/controllers/home_controller.rb
? To make this index file as the home page, 1st
we need to delete the
default public/index.html page
$ rm public/index.html
19

? Now, we have to tell Rails where your actual home page is located.
For that open the file config/routes.rb and edit as
root :to => "home#index"
? Check whether our home page is rendering proper page or not, for
that we need to start the rails serve as
$ rails s
20

Scaffolding
Rails scaffolding is a quick way to generate some of the major pieces
of an application. If you want to create the models, views, and
controllers for a new resource in a single operation, scaffolding is
the tool for the job.
Example:
Creating a Resource for sessionApp:
We can start by generating a scaffold for the Post resource: this will
represent a single blog posting.
$ rails generate scaffold Post name:string title:string content:text
21

File Purpose
db/migrate/20120606184725_create_po
sts.rb
Migration to create the posts table in
your database (your name will include a
different timestamp)
app/models/post.rb The Post model
config/routes.rb Edited to include routing information for
posts
app/controllers/posts_controller.rb The Posts controller
app/views/posts/index.html.erb A view to display an index of all posts
app/views/posts/edit.html.erb A view to edit an existing post
app/views/posts/show.html.erb A view to display a single post
app/views/posts/new.html.erb A view to create a new post
22

Running a Migration:
? Rails generate scaffold command create is a database migration.
Migrations are Ruby classes that are designed to make it simple to
create and modify database tables. Rails uses rake commands to
run migrations, and it��s possible to undo a migration ($ rake
db:migrate rollback) after it��s been applied to your database.
23

? If we look in the db/migrate/20120606184725_create_posts.rb
class CreatePosts < ActiveRecord::Migration
def change
create_table :posts do |t|
t.string :name
t.string :title
t.text :content
t.timestamps
end
end
? At this point, we can use a rake command to run the migration:
$ rake db:migrate
24

Rails will execute this migration command and tell you it created the
Posts table.
== CreatePosts: migrating
===================================================
=
-- create_table(:posts)
-> 0.0019s
== CreatePosts: migrated (0.0020s)
===========================================
25

Adding a Link:
? We can add a link to the home page. Open
app/views/home/index.html.erb and modify it as follows:
<h1>Hello, Rails!</h1>
<%= link_to "New Post", posts_path %>
When we run the server it displays the home page as
26

The Model:
? The model file, app/models/post.rb is
class Post < ActiveRecord::Base
attr_accessible :content, :name, :title
end
? Active Record supplies a great deal of functionality to our Rails
models for free, including basic database CRUD (Create, Read,
Update, Destroy) operations, data validation
27

Adding Some Validation:
? Rails includes methods to help you validate the data that you send to
models. Open the app/models/post.rb file and edit it:
class Post < ActiveRecord::Base
attr_accessible :content, :name, :title
validates :name, :presence => true
validates :title, :presence => true,
:length => {:minimum => 5}
end
28

Listing All Posts
? How the application is showing us the list of Posts.
? Open the file app/controllers/posts_controller.rb and look at the
index action:
def index
@posts = Post.all
respond_to do |format|
format.html # index.html.erb
format.json { render :json => @posts }
end
end
29

? The HTML format(format.html) looks for a view in
app/views/posts/ with a name that corresponds to the
action name(index). Rails makes all of the instance
variables from the action available to the view. Here��s
app/views/posts/index.html.erb:
30

<h1>Listing posts</h1>
<table>
<tr> <th>Name</th>
<th>Title</th>
<th>Content</th>
<th></th>
<th></th>
<th></th>
</tr>
<% @posts.each do |post| %>
<tr>
<td><%= post.name %></td>
<td><%= post.title %></td>
<td><%= post.content %></td>
<td><%= link_to 'Show', post %></td>
<td><%= link_to 'Edit', edit_post_path(post) %></td>
<td><%= link_to 'Destroy', post, :confirm => 'Are you sure?',
:method => :delete %></td>
</tr>
<% end %>
</table>
<br />
<%= link_to 'New post', new_post_path %>
31

Creating an App using spree:
? Spree is a full featured commerce platform written for the Ruby on
Rails framework. It is designed to make programming commerce
applications easier by making several assumptions about what most
developers needs to get started. Spree is a production ready store.
An Introduction to Ruby and Rails 32

? Now we are going to see how we create
e-commerce(spree) application.
$ rails new SpreeApp
$ cd SpreeApp
$ spree install
Would you like to install the default gateways? (yes/no) [yes] yes
Would you like to run the migrations? (yes/no) [yes] yes
Would you like to load the seed data? (yes/no) [yes] yes
Would you like to load the sample data? (yes/no) [yes] yes
Admin Email [spree@example.com]
Admin Password [spree123]
Would you like to precompile assets? (yes/no) [yes] yes
$ rails server

THANK YOU!
35

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Ruby on Rails introduction

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