Introduction to Ruby&Rails

Yuri Veremeyenko Monica Verma Introduction to Ruby&Rails

Presentation Structure • Ruby • Overview • Syntax • Rails • Introduction • What makes Rails a good choice? • Typical Web Request Flow • ROR and MVC • On-spot project creation • Basic application (blog)‏ • Scaffold, Migrations, Routing, etc. • Conclusions

Ruby - overview • Originally from Japan, first public version 1995 • Multipurpose: from scripting to fully fledged OO applications • Current Version : 1.8.7 • Web Site: http://www.ruby-lang.org/ • Ruby in your web browser: http://tryruby.hobix.com/

Ruby – syntax examples • Everything is an object 255.times {|i| puts "Hello #{i}" } • Arrays a = [1, 'hi', 3.14, 1, 2] a.reverse a.each { |x| puts x } • Hashes h = {:water => 'wet', :fire => 'hot'} h.each_pair do |key, value| puts "#{key} is #{value}"; end • Ranges (0..2).each {|i| puts i} #=> [0, 1, 2]

Ruby – syntax examples II • Exceptions • raise ArgumentError, • "Illegal arguments!” • ... • begin • # Do something • rescue • # Handle exception • end • Classes & Methods class Person attr_accessor :name, :age def initialize(name, age)‏ @name, @age = name, age end end p = Person.new("jay", 29)‏ p.name >> "jay”

Ruby – syntax examples III • Returning multiple parameters class MyClass < MyAbstractClass def my_method return 1, 2 end end a = MyClass.new b, c = a.my_method • Reflection a = MyClass.new a.public_methods a.respond_to? "mymethod"

Ruby on Rails • “an open source web framework that optimizes for programmer happiness and sustainable productivity” • This translates to: • Usage of MVC pattern • Scripts and generators for common actions • Use of Ruby's object nature • DRY (don't repeat yourself)‏ • Support for most Web 2.0 fancy stuff

ROR: installation • Ruby • The ruby interpreter (1.8.6 recommended)‏ • Gem • Gem is ruby package manager • Database (postgres / mysql / sqlite)‏ • Install as you would normally • Bind Ruby and your Database • Normally available as gem • Rails and other Gems and libs, as required • Libopenssl-ruby, ruport, rdoc, irb, etc.. • IDE

What are typical activities for web application? • Display form • Validate form • Display form errors • Save form • Show aggregated data (and more forms)‏

What makes ROR a good choice? • MVC • ORM (ActiveRecord with associations)‏ • Data validation standardized • Well structured application layout • Generators for common tasks • Testing support

ROR in typical web request Fig.1 Web request flow

ROR and MVC • Model : database logic, business data logic • Controller : request processing, couples View and Model • View : sets of templates to render HTML Fig.2 MVC in Rails

Generators and migrations • Generators can create skeletons for models/views/controllers/ or scaffold >ruby script/generate scaffold MyEntity • Migrations provide DB synchronization class CreatePosts < ActiveRecord::Migration def self.up create_table :posts do |t| { t.column :title, :string ; t.column :body, :text } end def self.down drop_table :posts ; end; end

Inside Rails Fig.3 Rails Model code

Example Application • A sample blog application in 20 minutes • Create Posts and Comments • Scaffolding, migrations, rake • Specifying relationships in Models • Customizing generated Controllers • Very basic HTML

Conclusions Ruby on Rails: • Is an MVC framework for Web application • Has efficient ActiveRecord ORM • Supports migrations • Has generators for common tasks • Supports unit testing • Provides AJAX support via prototype • RESTful since v2.0

Introduction to Ruby&Rails