Rails Intro & Tutorial

Ruby On Rails
Intro & Tutorial

Mason Chang

Saturday, April 13, 13

Who I am?

• Mason Chang (張銘軒)
• Works at OptimisDev
• twitter: @changmason
• github: https://github.com/changmason


Part I


What is Rails?


Rails is...

http://rubyonrails.org/


Rails is...

• Created by DHH of 37signals in 2004
• Extracted from product Basecamp
• Of course, written in Ruby


Rails Philosophy


Don't Repeat Yourself

• Code generators
• Rake tasks
• Extentions


Code generators

• Generate new project
• Generate models
• Generate controllers & views


Rake tasks

• Run tests
• Manipulate database
• Show useful info


Extensions

• Sensible core extensions
• Helper methods
• A lot of 3rd party gems


Convention over
Conﬁguration(1)

• Convention for environments
development, test and production
• Convention for organizing code
• Convention for organizing assets


Convention over
Conﬁguration(2)

• Convention for models
model names - table names
model attributes - record ﬁelds
• Convention for controllers & views
controller actions - view templates


MVC Architecture


http://betterexplained.com/articles/intermediate-rails-understanding-models-views-and-controllers/


RESTful Routes


Combine HTTP verb and path to
dispatch requests to corresponding
handlers (actions)

http://guides.rubyonrails.org/routing.html


A very simple blog
in 5 minute


Part II


ActiveRecord & Model


What is ActiveRecord?

• ORM, Object-Relational Mapping
• Dealing with SQL
• A standalone Module
• Tons of functionalities


$ gem install activerecord
$ irb

> require 'rubygems'
> require 'active_record'
> ActiveRecord::VERSION::STRING


ActiveRecord can
connect to existing DB
> ActiveRecord::Base.establish_connection(
:adapter => 'mysql2',
:database => 'fju_test_db',
:username => 'root',
:password => '******' )

> ActiveRecord::Base.connection

> ActiveRecord::Base.connected?


ActiveRecord can
migrate existing DB
> ARConnection = AR::Base.connection

> ARConnection.create_table(:users) do |t|
t.string :name
t.integer :age
t.timestamps
end

> ARConnection.add_index(:users, 'name')


ActiveRecord can
execute raw SQL
> ARConnection = AR::Base.connection

> ARConnection.execute(%q{
INSERT INTO users (name, age)
VALUES ('Mason Chang', 30)
})

> resultes = ARConnection.execute(%q{
SELECT * FROM users WHERE age = 30
})
> results.fields
> results.first


User Model

> class User < ActiveRecord::Base
end

> require 'logger'

> ActiveRecord::Base.logger =
Logger.new(STDOUT)


Model can create
records
> user.newser = User.new(
:name => 'Eddie Kao', :age => 20)
> user.save

> User.create(
:name => 'Ryudo Teng', :age => 20)


Model can retrieve
records
> User.first

> User.last

> User.all

> User.find(1)

> User.find([1,2,3])

> User.find(:first,
:conditions => {:name => 'Eddie Kao'})

> User.find(:all,
:conditions => ['age < ?', 30])


Model can update
records
> user = User.find_by_name('Mason Chang')
> user.age = 10
> user.save

> user.update_attribute(:age, 20)

> user.update_attributes(
:name => 'Ming-hsuan Chang'
:age => 30)

> User.update(1, :age => 40)

> User.update_all(
{:age => 50}, ['age >= ?', 20])


Model can delete
records
> user = User.first

> user.delete # callbacks ignored

> user.destroy # callbacks triggered

> User.delete(1) # callbacks ignored

> User.destroy(1) # callbacks triggered


Model can do
validations
> class User
validates_presence_of :name
validates_numericality_of :age
end

> user = User.new(:age => 'thirty")

> user.save # fail

> user.errors.messages

http://guides.rubyonrails.org/active_record_validations_callbacks.html


Model can have
callbacks
• Callbacks are operations which hooked
into the lifecycle of an ActiveRecord object
• Object's lifecycle includes:
creating, updating and destroying an object
after initializing and ﬁnding an object

http://guides.rubyonrails.org/active_record_validations_callbacks.html


Callbacks for creating
an object
• before_validation

• after_validation

• before_save

• around_save

• before_create

• around_create

• after_create

• after_save


Callbacks for updating
an object
• before_validation

• after_validation

• before_save

• around_save

• before_update

• around_update

• after_update

• after_save


Callbacks for
destroying an object

• before_destroy

• around_destroy

• after_destroy


Model can have
associations
• One-to-one
• One-to-many
• Many-to-many
• and more...

http://guides.rubyonrails.org/association_basics.html


One-to-one association


One-to-many
association


Many-to-many
association


Part III


Task 0: Install Rails


$ gem install rails

$ rails --version


The rails command
• create new project
> rails new [project_name]

• start server
> rails server

• start console
> rails console

• execute generator
> rails generate [generator_type]

• more, and get help
> rails help [command]


Task 1: New Project


$ rails new mylibrary
--skip-test-unit

$ cd mylibrary/

$ rails server

$ rm public/index.html


Project Directory(1)


Project Directory(2)


Task 2: Install Some
Gems & Import Specs


Gemfile: add haml-rails gem

$ bundle install

Gemfile: add rspec-rails

Gemfile: add capybara

$ bundle install

$ rails generate rspec:install

spec/spec_helper.rb:
require 'capybara-rails'


Task 3: Create Book
Model


$ rails generate model Book
author:string
title:string
description:text
publish_date:date

$ rake db:migrate

$ rails console

> Book.column_names


Task 4: Pass the
"Create" Book Spec


Task 5: Pass the
"Retrieve" Book Spec


Task 6: Pass the
"Update" Book Spec


Task 7: Pass the
"Destroy" Book Spec


Task 8: Refactor Routes


Task 9: Refactor Views


Task 10: Scaffold the
Category


$ rails generate model Category
name:string

$ rake db:migrate

$ rails console

> Category.column_names


Task 11: Apply Models'
Associations


class Category < ActiveRecord::Base

has_many :books

end

class Book < ActiveRecord::Base

belongs_to :category

end


$ rails generate migration
add_category_id_to_books
category_id:integer:index

$ rake db:migrate


Task 12: Validate Inputs


class Book < ActiveRecord::Base

belongs_to :category

validates_presence_of :category_id,

:author,

:title

end


Task 13: Decorate
with Twitter Bootstrap


Task 14: Deploy to
Heroku


Assignments


Assignment 1:
Add a search bar above the book list
table on the index page, so the user can
search for books by author name or by
book title.


Assignment 2:
Add pagination links below the book
list table on the index page, so the user
can browse through 20 books per page.


Rails Intro & Tutorial

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