1. Ruby on Rails: An Introduction JA-SIG Summer Conference 2007 Michael Irion The University of Tulsa

2. What is Ruby on Rails (RoR)? Ruby on Rails is an open-source, full-stack framework for developing database-backed web applications according to the Model-View-Control pattern

3. Overview of Ruby on Rails Ruby is the programming language used to manipulate the framework Rails is the framework that provides the necessary infrastructure Rails is written in Ruby

4. Ruby Features Ruby is an interpreted language (No compile step necessary) Ruby is an Object Oriented language. Everything is an object (No primitives) Ruby draws from Perl, Smalltalk, and Lisp

5. Duck Typing in Ruby Objects are dynamic, and their types are determined at runtime The type of a Ruby object is much less important than it’s capabilities If a Ruby object walks like a duck and talks like a duck, then it can be treated as a duck

6. Rails Philosophy Convention over configuration (no XML) Don’t Repeat Yourself (DRY) Rails is opinionated

7. Rails Architecture Rails applications are implemented using the Model- View-Controller (MVC) Model - ActiveRecord View - ActionView Controller - ActionController

8. Starting the Bookmarks Application Generate application > rails bookmarks

9. Directory Layout Rails applications have a common directory structure /app - the MVC core /controllers /helpers - provides extra functionality for views /models /views/nameofcontroller - templates for controller actions

10. Directory Layout /components - will be deprecated /config - database, route and environment configuration /db - database schema and migrations /lib - functions that don’t map to MVC /log /public - static web resources (html, css, javascript etc.) /script - rails utilities /test - tests and fixtures /tmp /vendor - 3rd party plugins

11. Rails Environment Modes Rails runs in different modes, depending on the parameters given to the server on startup. Each mode defaults to it’s own database schema Development (verbose logging and error messages) Test Production

12. Starting Rails > cd /directorypath/bookmarks Start the server > ruby script/server start Default environment is development Default port is 3000 http://127.0.0.1:3000

13. Welcome Aboard - Now What? Hello world seems appropriate >ruby script/generate controller hello exists app/controllers/ exists app/helpers/ create app/views/hello exists test/functional/ create app/controllers/hello_controller.rb create test/functional/hello_controller_test.rb create app/helpers/hello_helper.rb

14. Mapping URLs to Controllers and Actions http://127.0.0.1:3000/hello/sayit http://127.0.0.1:3000 - address and port of the webserver http://127.0.0.1:3000 hello - name of the controller sayit - name of the action (method in controller)

15. Editing the Controller def sayit render :text => " Hello World! " end

16. Now for an actual Bookmark Edit config/database.yml development: adapter: mysql database: bookmarks_development username: username password: password host: localhost

17. Create the Database This step depends on the database and dba tool of your choice. Create a new schema/dbname for bookmarks_development, and assign rights for the user you listed in database.yml.

18. Bookmark Model Our bookmark model will (initially) need two properties URL Title

19. Scaffolding for Bookmarks Rails can generate all the basic CRUD operations for simple models via scaffolding. Scaffolding is temporary way to get applications wired quickly. > ruby script/generate scaffold_resource bookmark url:string title:string

20. Migrations Rails uses migrations to version the database. Rails tries to minimize SQL at every opportunity Migrations are automatically created whenever you generate a new model Migration files are located in db/migrations The version number is stored in a table called schema_info

21. Bookmarks Migration located in db/migrate/001_create_bookmarks.rb class CreateBookmarks < ActiveRecord::Migration def self.up create_table :bookmarks do |t| t.column :url, :string t.column :title, :string end def self.down drop_table :bookmarks end

22. Running the Migration Rake is the general purpose build tool for rails, much like make, or ant. It has many functions, one of which is to control migrations. >rake db:migrate Now the table has been created

23. Bookmarks Table ID Bookmarks table has the following fields - id, url, and title Where did the id field come from? Convention of configuration - Rails automatically creates an id field for each new table and uses it as the primary key

24. Bookmarks Controller The /app/controllers/bookmarks.rb default action: def index @bookmarks = Bookmark.find(:all) respond_to do |format| format.html # index.rhtml format.xml { render :xml => @bookmarks.to_xml } end End

25. Mapping URLs to Controllers and Actions http://127.0.0.1:3000/bookmarks/ http://127.0.0.1:3000 - address and port of the webserver http://127.0.0.1:3000 hello - name of the controller / - name of the action (blank maps to the index action)

26. Bookmarks Model - Don’t Repeat Yourself No getters/setters. Rails uses information from the database. class Bookmark < ActiveRecord::Base end

27. Bookmarks View Located in views/bookmarks/index.rhtml 'Are you sure?', :method => :delete %>

28. Convention over Configuration Bookmark model automatically looks for a table in the database with a plural form of it’s name. (bookmarks) The Bookmarks controller automatically renders the template located in views according to the controller name and the action (views/bookmarks/index.rhtml)

29. Ajax Helpers Rails allows you to program many AJAX calls in ruby, instead of writing javascript directly Script.aculo.us and Prototype libraries are included A quick example. Autocomplete for text boxes

30. AJAX Autocomplete Add to Bookmarks controller auto_complete_for :bookmarks, :url Add to views/bookmarks/edit.rhtml In views/layouts/bookmarks.rhtml, add

31. Validations Rails has a number of validation helpers that can be added to the model. class Bookmark < ActiveRecord::Base validates_presence_of :url, :title end

32. Validations validates_presence_of validates_length_of validates_acceptance_of validates_confirmation_of validates_uniqueness_of validates_format_of validates_numericality_of validates_inclusion_in validates_exclusion_of validates_associated :relation

33. Associations - Adding Categories to Bookmarks The bookmarks are working great, but it would be nice if we could group them by category Rails uses associations to build relationships between tables Associations are independent of database foreign key constraints

34. Types of Associations has_one belongs_to has_many has_and_belongs_to_many has_many :model1, :through => :model2

35. Changes to the Database A new categories table needs to be created A category_id field needs to be added to the bookmarks table > ruby script/generate scaffold_resource category name:string This creates the all the scaffolding and the migration db/migrate/002_create_categories.rb Note the category table is pluralized as categories. >ruby script/generate migration alter_bookmarks_add_category_id This creates db/migrate/003_alter_bookmarks_add_category_id.rb

36. Alter Bookmarks Migration def self.up add_column :bookmarks, :category_id, :integer end def self.down remove_column :bookmarks, :category_id end >rake db:migrate

37. Types of Associations has_one belongs_to has_many has_and_belongs_to_many has_many :model1, :through => :model2

38. Database Relationships Parent (or Master) models that have collections of other models use the has_many relationship Child (or Detail) models contain the id field of their parent record and they use the belongs_to relationship

39. Associations Model Code class Bookmark < ActiveRecord::Base validates_presence_of :url, :title belongs_to :category end class Category < ActiveRecord::Base has_many :bookmarks end

40. Associations Controller code def edit @bookmark = Bookmark.find(params[:id]) @categories = Category.find(:all) end

41. Associations View Code Category

42. Tools Textmate (Mac OS X) RadRails (Eclipse plugin) www.radrails.orgwww.radrails.org Other commercial and opensource IDEs are being made available

43. Resources Programming Ruby: The Pragmatic Programmers' Guide - Second Edition Agile Web Development with Rails—Second Edition Rails main site http://www.rubyonrails.comhttp://www.rubyonrails.com My email: michael-irion@utulsa.edu