Introduction to Ruby&Rails Yuri Veremeyenko Monica Verma

Presentation Structure 1.Ruby –Overview –Syntax 2.Rails –Introduction –What makes Rails a good choice? –Typical Web Request Flow –ROR and MVC 3.On-spot project creation –Basic application (blog)‏ –Scaffold, Migrations, Routing, etc. 4.Conclusions

Ruby - overview Originally from Japan, first public version 1995 Multipurpose: from scripting to fully fledged OO applications Current Version : Web Site: Ruby in your web browser:

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

Ruby – syntax examples III Returning multiple parameters class MyClass < MyAbstractClass def my_method return 1, 2 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