A getting started guide to rails version 2.3.5

1. Rails
Beginners Guide

2. Rails
• Web application framework written in ruby
• Based on Model View Controller architecture (MVC)
• Uses core APIs and generators to
– reduce the coding burden and
– focus your efforts on value-adding development
• Large community of developers
– Provide support to each other
– Write gems (libraries) to extend the framework (see
rubygems.org)
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3. Why Rails
• Productive
– Programming in Ruby is simpler
– Boiler plate already in place (e.g. binding objects between
tiers)
– Gems for re-usable features
• Each to understand
– Convention over configuration
– Configuration-like programming e.g. ActiveRecord
• Large community
• Matur(e/ing)
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4. Setup
Getting your environment ready

5. Install
• MySQL 5.X
• HeidiSQL (SQL Client)
• Ruby 1.8.7
– http://www.ruby-lang.org/en/downloads/
– Note version
• Rails
– gem install rails –v=2.3.5
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6. Project Setup
• Create a database
– mysql –u root -p
– create database library;
– GRANT ALL ON library.* TO ‘library’@’localhost’ IDENTIFIED
BY ‘library ‘;
– FLUSH PRIVILEGES;
• Create a rails application
– rails library
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7. Project Setup
• Configure your application to communicate to the
database
– config/database.yml
• development:
• adapter: mysql
• database: library
• username: library
• password: library
• host: localhost
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8. Concepts
High-level Overview

9. Concepts
• Rake
• Routes
• Migrations
• Generators
• Object relationships
• Validates
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10. Rake
• Rake is ruby’s build program (similar to make and ant)
• Rake uses rakefiles to manage the build
– Written in ruby
– Default one created for rails which includes standard tasks
• Rake tasks are namespaced
• To see all the available rake tasks run rake –T or rake –
tasks
• Most commonly used rake tasks
– rake db:migrate – migrate the database to the current
version
– rake db:rollback – move the database back a version
– rake test – run all tests (unit tests and functional tests)
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11. Routes
• The rails router matches incoming requests to
controller actions
• Routes are configured in config/routes.rb
• Some generators add routes e.g. ruby script/generate
scaffold cd name:string artist:string genre:string
– Will add routes to add, delete, update, show, list posts
• Routes can also be used to generate URLs for links,
forms e.g.
– link_to @cd.name, cd_path(@cd) – creates a link to the post
show page
• The routes API supports a multitude of operations, a
common ones is:
– map.resources :cds – creates CRUDL routes
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12. Migrations
• Migrations allow you to manage a database through
versions
• Each version is held in a separate timestamp prefixed
file in db/migrate
• Each migration knows how to update the database
(self.up) and how to rollback (self.down)
• Migrations are written in ruby and the migrations api
supports a wide range of table and column alterations
• You can also run normal SQL and ruby code
• Every time a migration is run the <table> table is
updated to include the timestamp
• Migrations with rake db:migrate and rake db:rollback
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13. Generators
• Command line interface to run code generators
• Rails comes with a set of out of the box templates
– You can customise these
– You can add your own
• Typically generate classes into your app directory e.g.
– ruby script/generate model cd name:string artist:string
genre:string – generates a model and associated files (tests,
migrations) with the attributes specified
– ruby script/generate scaffold cd name:string artist:string
genre:string - creates not only the model but also a CRUDL
controller and views
– ruby script/generate migration add_record_label_to_cd –
creates a single migration
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14. Object relationships
• ActiveRecord is ruby implementation of the active
record pattern (Martin Fowler 2003)
• Set of meta-programming methods allow you to
configure relationships in your model objects:
– belongs_to :cd - for table holding pkey
– has_many :tracks - notice the plural, for connected table
– has_many :genres, :through => :cd_genres – to link
through a relationship table
• Then you can call methods on your model objects e.g.
• @cd.tracks # array of tracks
• @cd.genres # array of genres
• @track.cd # cd model object
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15. Validations
• Rails makes a set of validation methods available
• Configure them in your model object
• Rails validates on save and stores and saves it in
<object>.errors
• Some examples:
– validates_presence_of :title, :artist – mandatory field checks
– validates_uniqueness_of :title – each title can only be used
once
– validates_numericality_of :quantity – must be a number
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16. Console
• Console lets you run your application through the
command line and test out pieces of code
• To start a console session
– ruby script/console
• From there you can run ruby commands and will have
access to all of your objects
• The console saves a lot of time loading and reloading
web pages to test functionality
• Some useful commands
– _ - provides access to the last result e.g. @cd = _
– puts @cd.to_yaml (or y @cd) – writes out an indented
version of the object
– reload! – reload the app
– <tab> - autocompletes methods
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17. Simple Project
A CD library

18. Create your model and scaffold
• rails library
• cd library
• ruby script/generate scaffold cd name:string
artist:string genre:string
• rake db:migrate
• ruby script/server
• http://localhost:3000/cds
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19. Create relationships between models
• ruby script/generate scaffold track name:string
cd_id:integer
• rake db:migrate
• Create associations in the model classes
– track.rb - belongs_to :cd
– cd.rb - has_many :track
• Allow tracks to select an album in track/edit.html.erb
– <%= select( “track", “cd_id", Cd.all.map {|cd| [cd.name,
cd.id]}, { :include_blank => "No part of an album" }, {:class
=> "fieldSelect"}) %>
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20. Next
Where to go next

21. Taking a step beyond the basics
• Access other people’s shared code via gems and plugins
– authlogic – controllers and UI to enable authentication
– will_paginate – rich pagination for lists
– cucumber – behaviour driven testing
– faker – data generator
– paperclip – file attachments
• Caching – Rails.cache.read/write/delete and config for
cache setup
• Deployment with capistrano
• Ajax via jQuery and format.js
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22. References
Useful links

23. Further reading and videos
• Railscasts – http://www.railscasts.com
– Video tutorials from Ryan Bates
• Pivotal Labs - http://pivotallabs.com/talks
– Wide range of talks including rails from leading tech company
• has_many :through blog -
http://blog.hasmanythrough.com/
– John Susser’s blog, senior rails developer at Pivotal Labs
• Ruby Doc - http://www.ruby-doc.org/
– Ruby class documentation
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