Ruby on Rails at PROMPT ISEL '11

Web Development with

Ruby On Rails

Pedro Cunha

Ruby

Yukihiro "Matz" Matsumoto
Ruby is designed for programmer
productivity and fun

Created February 1993

Ruby
Everything is an object Dynamic Typing

true.class # TrueClass class Fooâ€¨
nil.class # NilClass def initialize(x, y)â€¨
@x = x
@y = y
end
end

class Foo2
end

Foo.new(2, Foo2.new)

Ruby
class Foo class Bar
# Parenthesis can be omitted # Use ! if you change self
def method def method!
puts "Hello World" end
end
# Use ? if you return a boolean
# Default params def method?
def method2(x = 2) end
puts x
end # Only conventions
end
# Operator overload
def +(x)
end
end

Ruby
"hello".class # String
:hello.class # Symbol a = "Hello"
b = "Hello"
# Convention
# Use string if you plan to a.equal? b # false
compute text
x = :hello
# Use symbols if you want to y = :hello
define or/and set a
behaviour which is not x.equal? y # true
expected to change

Ruby
a = {}
a[:first] = 2
a[:things] = 3
a[:foo] = "bar"

b = {
:first => 2,
:things => 3,
:foo => "bar"
}

b[:first] # 2

Ruby
x = [1,4,5,2,5,8,10]

x.sort # returns a copy of x sorted
[1,2,4,5,5,8,10]
x.sort! # modifies self

x.map{ |i| i + 4 } # [5,6,8,9,9,12,14]
x.map! do |i|
i + 4
end # [5,6,8,9,9,12,14]

Ruby
Monkey Patching

class String
def +()
# override string default + operator
end
end

“With great power comes great responsability”
Uncle Ben, Amazing Spiderman nº1

Ruby on Rails
Created by David Heinemeir Hansson
• CEO at 37th Signals
• Personal Project, 2004
Present
• Rails 3.1
• Growing community

Ruby on Rails

Convention vs Conﬁguration
MVC Architecture
REST routing

• Don’t Repeat Yourself
• Increased productivity through
conventions. Ex.: following a pattern for
foreign key columns.

• Take advantage of singular and plural word
meanings

REST
Representational State Transfer

CRUD REST ROUTES

CREATE POST /posts
READ GET /posts/1
UPDATE PUT /posts/1
DELETE DELETE /posts/1

# routes.rb
Blog::Application.routes.draw do
resources :posts
end

pcunha:prompt$ rails new Blog -d mysql

Blog
/app
/controllers
/mailers
/models
/views
/config
database.yml
/db
/migrate
Gemfile
/public
/javascripts
/stylesheets

# config/database.yml
development:
adapter: sqlite3
database: db/development.sqlite3

test:
adapter: sqlite3
database: db/test.sqlite3

production:
adapter: sqlite3
database: db/production.sqlite3

development:
adapter: mysql2
encoding: utf8
database: Blog_development
username: root
password:

test:
adapter: mysql2
encoding: utf8
database: Blog_test
username: root
password:

production:
adapter: mysql2
encoding: utf8
database: Blog_production
username: root
password: rails new with mysql option

pcunha:Blog$ rails server

=> Booting WEBrick
=> Rails 3.0.7 application starting in
development on http://0.0.0.0:3000
=> Call with -d to detach
=> Ctrl-C to shutdown server

pcunha:Blog$ rails generate scaffold Post title:string body:text

invoke active_record
create db/migrate/20110715102126_create_posts.rb
create app/models/post.rb
invoke test_unit
create test/unit/post_test.rb
create test/fixtures/posts.yml
invoke scaffold_controller
create app/controllers/posts_controller.rb
invoke erb
create app/views/posts
create app/views/posts/index.html.erb
create app/views/posts/edit.html.erb
create app/views/posts/show.html.erb
create app/views/posts/new.html.erb
create app/views/posts/_form.html.erb

# config/db/migrate/20110715102126_create_posts.rb
class CreatePosts < ActiveRecord::Migration
def self.up
create_table :posts do |t|
t.string :title
t.text :body

t.timestamps
end
end

def self.down
drop_table :posts
end
end

pcunha:Blog$ rake db:create
pcunha:Blog$ rake db:migrate
== CreatePosts: migrating
-- create_table(:posts)
-> 0.0015s
== CreatePosts: migrated (0.0018s)

pcunha:Blog$ rails generate model Comment body:text

create db/migrate/20110715103725_create_comments.rb
create app/models/comment.rb
invoke test_unit
create test/unit/comment_test.rb
create test/fixtures/comments.yml

pcunha:Blog$ rails generate migration AddPostIdToComments
post_id:integer

create db/migrate/20110715103834_add_post_id_to_comments.rb

# 20110715103834_add_post_id_to_comments.rb
class AddPostIdToComments < ActiveRecord::Migration
def self.up
add_column :comments, :post_id, :integer
end

def self.down
remove_column :comments, :post_id
end
end

pcunha:Blog$ rake db:migrate
== CreateComments: migrating
-- create_table(:comments)
-> 0.0011s
== CreateComments: migrated (0.0012s)

== AddPostIdToComments: migrating
-- add_column(:comments, :post_id, :integer)
-> 0.0011s
== AddPostIdToComments: migrated (0.0041s)

rake db:create
rake db:migrate
rake db:migrate:redo
rake db:rollback

blog_db.schema_migrations
- keeps the version number of all
migrations already runned

# app/models/post.rb
class Post < ActiveRecord::Base
has_many :comments
end

# app/models/comment.rb
class Comment < ActiveRecord::Base
belongs_to :post
end

Post.all
Post.find(1).comments
Comments.find(1).post
Post.order(:created_at)
Post.limit(5).offset(2)

# app/models/post.rb
class Post < ActiveRecord::Base
has_many :comments

validates_presence_of :title
validates_format_of :title, :with => /ASLB.*z/
end

p = Post.new
p.save # false
p.errors.full_messages # ["Title can't be blank", "Title
is invalid"]

p.title = "SLB is the best"
p.save # true

validates_presence_of :nif

validates_format_of :name

validates_acceptance_of :terms_and_conditions, :on => :create

validates_numericality_of :age, :greater_than_or_equal_to => 18

validates_uniqueness_of :model_fk_key, :scope => :model_fk_key2

validates_length_of :minimum => 5

Controllers
Managing the CRUD

# app/controllers/posts_controller.rb
class PostsController < ApplicationController
# GET /posts
def index ...

# GET /posts/1
def show ...

# GET /posts/new
def new ...

# GET /posts/1/edit
def edit ...

# POST /posts
def create ...

# PUT /posts/1
def update ...

# DELETE /posts/1
def destroy ...
end
Generated with scaffold

# POST /posts
# POST /posts.xml
def create
@post = Post.new(params[:post])

respond_to do |format|
if @post.save
format.html { redirect_to(@post, :notice => 'Post was
successfully created.') }
format.xml { render :xml => @post, :status
=> :created, :location => @post }
else
format.html { render :action => "new" }
format.xml { render :xml => @post.errors, :status
=> :unprocessable_entity }
end
end
end

def index
@posts = Post.all

format.html # index.html.erb
format.xml { render :xml => @posts }
end
end

pcunha:Blog$ curl http://localhost:3000/posts.xml
<?xml version="1.0" encoding="UTF-8"?>
<posts type="array">
<post>
<created-at type="datetime">2011-07-15T13:39:51Z</created-at>
<body>This is the body of the first post</body>
<title>The first very post of this blog</title>
<updated-at type="datetime">2011-07-15T13:39:51Z</updated-at>
<id type="integer">1</id>
</post>
</posts>

# app/views/posts/new.html.erb
<h1>New post</h1>

<%= form_for(@post) do |f| %>
def new <div class="field">
@post = Post.new <%= f.label :title %><br />
respond_to do |format| <%= f.text_field :title %>
format.html # new.html.erb} </div>
end <div class="field">
<%= f.label :body %><br />
end
<%= f.text_area :body %>
</div>
<div class="actions">
<%= f.submit %>
</div>
<% end %>

<%= link_to 'Back', posts_path %>

# app/views/posts/edit.html.erb
<h1>Edit post</h1>


<div class="field">
<%= f.label :title %><br />
<%= f.text_field :title %>
def edit </div>
@post = Post.find(params[:id]) <div class="field">
respond_to do |format| <%= f.label :body %><br />
format.html # edit.html.erb} <%= f.text_area :body %>
end </div>
end
<%= f.submit %>
</div>
<% end %>

<%= link_to 'Show', @post %> |

Rails builds the route for you

link_to 'Show', @post # GET posts/@post.id

form_for(@post)

if @post.new_record?
POST /posts
else
PUT /posts/@post.id
end

# app/views/posts/new.html.erb # app/views/posts/edit.html.erb
<h1>New post</h1> <h1>Edit post</h1>

<%= form_for(@post) do |f| %> <%= form_for(@post) do |f| %>

<div class="field"> <div class="field">
<%= f.label :title %><br /> <%= f.label :title %><br />
<%= f.text_field :title %> <%= f.text_field :title %>
</div> </div>
<div class="field"> <div class="field">
<%= f.label :body %><br /> <%= f.label :body %><br />
<%= f.text_area :body %> <%= f.text_area :body %>
</div> </div>
<div class="actions"> <div class="actions">
<%= f.submit %> <%= f.submit %>
</div> </div>
<% end %> <% end %>

<%= link_to 'Back', posts_path %> <%= link_to 'Show', @post %> |

Bad pattern

# app/views/posts/_form.html.erb
# app/views/posts/new.html.erb
<h1>New post</h1>

<div class="field">
<%= render "form" %>%>
<%= f.label :title %><br />
<%= f.text_field :title %>
</div>
<div class="field">
# app/views/posts/edit.html.erb
<h1>Edit post</h1>
</div>
<%= render "form" %>%>
<%= f.submit %>
<%= link_to 'Show', @post %> |
</div>
<% end %>

The right way

Improve user experience by not having the
whole page reload when submitting a form
or simple pagination link

Also save resources used (SQL queries,
memory, more bandwidth usage,... etc)

AJAX
Changing default forms to AJAX

# config/routes.rb
Blog::Application.routes.draw do
resources :posts do
resources :comments, :only => [:create]
end
end

POST /posts/:post_id/comments

Limiting actions is always the best practice

# app/controllers/comments_controller.rb
class CommentsController < ApplicationController

def create
@post = Post.find(params[:post_id])
@comment = @post.comments.new(params[:comment])

if @comment.save
format.html { redirect_to(@post }
else
format.html { render :template => "posts/
show.html.erb" }
end
end
end
end

# app/views/posts/show.html.erb
...
<h1>Comments</h1>
<div id="comments">
<%= render :partial => "comments/comment",
:collection => @post.commments %>
</div>

<%= render :partial => "comments/form",
:locals => {
:post => @post,
:comment => @comment || Comment.new } %>

# app/views/comments/_form.html.erb
<%= form_for [post,comment] do |f| %>
<div class="field">

<p><%= f.submit %></p>
</div>
<% end %>

Our HTML form
What needs to change?

# app/views/comments/_form.html.erb
<%= form_for [post,comment], :remote => true do |f| %>
<div class="field">

<p><%= f.submit %></p>
</div>
<% end %>

That’s it? Not yet!

# app/controllers/comments_controller.rb
class CommentsController < ApplicationController

def create
@post = Post.find(params[:post_id])
@comment = @post.comments.new(params[:comment])

if @comment.save
format.html { redirect_to(@post, :notice => 'Comment was
successfully created.') }
format.js
else
format.html { render :action => "new" }
format.js
end
end
end
end

# app/views/comments/create.js.erb
//Dump javascript here!
document.getElementById...

Notice:
- create.js.erb
- writing native javascript is not optimal:
1. You will forget something about IE
2. We are at 21st Century
3. Lots of good frameworks

Rails 2.X and 3.0.X

- Prototype JS Framework as default

Rails 3.1 (released 2011)

- jQuery JS Framework as default

# app/views/comments/create.js.erb
<% if @comment.new_record? %>

<% content = render(:partial => "comments/form",
:locals => {
:post => @post,
:comment => @comment })
content = escape_javascript(content)
%>

$('new_comment').replace("<%= content %>");

<% else %>
<% comment_content = render(:partial => "comments/comment", :object => @comment)
comment_content = escape_javascript(comment_content)
%>

$('comments').insert({
bottom : '<%= comment_content %>'
})

$('new_comment').reset();
<% end %>

Almost there... but

- Complex code
- We can do better with Rails

RJS
Ruby (to) JavaScript Templates

# app/views/comments/create.js.rjs
if @comment.new_record?
page.replace :new_comment,
:partial => "comments/form",
:locals => {
:post => @post,
:comment => @comment }
else
page.insert_html :bottom, :comments, :partial
=> "comments/comment", :object => @comment
page[:new_comment].reset
end

Gems
Extend Rails framework

Easy installation and usage

Increasing community

• Github
• Gemcutter

Bundler gem
# Gemfile
gem "rails", "2.3.10"
gem "will_paginate"
gem "authlogic"

gem "pg"
gem "postgis_adapter", "0.7.8"
gem "GeoRuby", "1.3.4"

# Sphinx
gem "thinking-sphinx", "1.4.5"

group :development do
gem "capistrano"
gem "capistrano-ext"
gem "ruby-debug"
gem "wirble"
gem "mongrel"
end

References

http://rubyonrails.org/
http://railsapi.com/
http://railscasts.com/
http://railsforzombies.org/

Thanks :)
pedro.cunha@rupeal.com
@mryise

Ruby on Rails at PROMPT ISEL '11

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