Introduction to Ruby on Rails

Introduction to Ruby on Rails

Agnieszka Figiel
blog.agnessa.eu

Kraków Ruby Users Group
May 19th 2007

Design Principles MVC architecture Agile Development Usability and Success Stories Community and Resources

Ruby on Rails

quot;Rails is a full-stack framework for developing
database-backed web applications according to the
Model-View-Control pattern.quot;
www.rubyonrails.org - Ruby on Rails ofﬁcial site

2005 David Heinemeier Hansson

opinionated software: quot;it’s a very pragmatic, very targeted
framework with a strong sense of direction. You might not
share its vision, but it undeniably has one.quot;
DHH for Linux Journal (http://www.linuxjournal.com/article/8686)



Outline

Design Principles

MVC architecture

Agile Development

Usability and Success Stories

Community and Resources



Design Principles

MVC architecture

Agile Development

Usability and Success Stories

Community and Resources



Model - View - Controller

separate data (model) from user interface (view)

Model
data access and business logic
independent of the view and controller
View
data presentation and user interaction
read-only access to the model
Controller
handling events
operating on model and view



Database Persistance

OR mapping
Active Record design pattern
migrations
incremental schema management
multiple db adapters
MySQL, PostgreSQL, SQLite, SQL Server, IBM DB2,
Informix, Oracle, Firebird/Interbase, LDAP, SybaseASA



Full Stack Framework

MVC suite
built-in webserver
default db adapter
integrated logger
AJAX, web services, email
test framework
plugins



Convention over Configuration

fixed directory structure
everything has its place – source files, libs, plugins,
database files, documentation etc
file naming conventions
e.g. camel case class name, underscore file name
database naming conventions
table names, primary and foreign keys
standard configuration files
e.g. database connections, environment setting definitions
(development, production, test)



DRY - Don’t Repeat Yourself

reusing code
e.g. view elements
reusing data
e.g. no need to declare table ﬁeld names – can be read
from the database
making each line of code work harder
e.g. mini languages for speciﬁc domains, like
object-relational mapping
metaprogramming
dynamically created methods



Model - ActiveRecord

conventions:
name based OR mapping: mice db table -> Mouse class
primary key: auto-incremented numeric field called quot;idquot;
foreign key: quot;[singular_of_foreign_table_name]_idquot;, e.g.
quot;cat_idquot;
dynamic getters, setters, finders
dynamic means the existance of a field in db is enough to
manipulate it, e.g. dynamic getter like: mouse.name
abstracted db operations - create, update, destroy, find, ...
possible to use raw sql, but usually unnecessary, e.g.:
Mouse.find(:all, :include => {:mouse_holes},
:conditions => quot;location = ’shed’quot;,
:order => quot;namequot;, :limit => 10)



Model - ActiveRecord
support for basic entity relations (1:1, 1:n, n:n) with
dynamic accessors
backyard_mouse_hole.mice #=> Array of Mouse objects
parametrised queries against SQL injection, e.g. ﬁnd all
mice whose name is sth entered by the user:
Mouse.find(:all, :conditions => [quot;name = ?quot;,
mouse_name)

validators: an object won’t be saved in db unless it passes
all validation rules, e.g. uniqueness of a given ﬁeld:
validates_uniqueness_of :login
object life cycle callbacks, e.g.
before_create, before_save
Single Table Inheritance, polymorphic associations


View - ActionView

multiple template types
oldest and basic: erb (embedded ruby), similar to e.g. jsp
remote javascript templates
xml templates
easy reuse of view elements
ﬁle inclusion – layouts, templates, partials
multiple standard quot;helpersquot; – common html element
generators (e.g. form elements, paginators)
ridiculously easy AJAX integration – prototype,
scriptaculous



Controller - ActionController
all actions grouped logically in controller objects (actions
are public methods of the controller class)
conventions
name based url – action mapping
e.g. url: myhost.com/mice/show/1
action: ’show’ action in MiceController, params: id=1
name based action - template file mapping
e.g. action ’show’ in MiceController - template file
app/views/mice/show.rhtml
can be organised in an inheritance hierarchy
reduces code duplication and simplifies code
action callbacks –
before_filter, after_filter, around_filter
built-in mechanism of url rewrites – routes
easy access to request data, session, cookies


Rapid Development

built-in webserver
generators – save the ﬁngers
scaffold – kick-off start
plugins, libraries, tons of contributed code



Debugging

verbose log output
breakpoint debugger
script/console



Testing

test database + ﬁxtures
unit tests - tests for models
functional - tests for controllers
integration - tests for workﬂow
testing directly in browser - Selenium



Agile Project Heartbeat

test coverage - rcov
continuous integration
iterative db schema control - migrations
automated deployment - capistrano



Platform Independence

win, lin, mac
Apache, Lighttpd, mongrel
gem package manager



IDEs

textmate
vim
RadRails, Eclipse + RDT, Aptana
plugins for Idea, NetBeans
SCiTe
jEdit



Scaling

it scales – a must-see slideshow about scaling twitter (600
req/s!): http://www.slideshare.net/Blaine/scaling-twitter
view caching
page caching
action caching
fragment caching
sql caching
memcached
shared nothing architecture - multiplying application
servers



Hosting

http://wiki.rubyonrails.org/rails/pages/RailsWebHosts
US - a variety of shared hosting offers
Poland - poor shared hosting options hosted.pl
Root VPS



Success Stories

several ror powered high trafﬁc sites
http://twitter.com/ - community site
http://www.odeo.com/ - music sharing
http://www.43things.com/, http://www.43places.com/,
http://www.43people.com/
37Signals: BaseCamp, BackPack, Ta-Da List, Writeboard,
CampFire
http://www.strongspace.com/ - storing and sharing ﬁles



Books

in English:
ruby: quot;Programming Ruby 2nd Editionquot; (the Pickaxe) Dave
Thomas, with Chad Fowler and Andy Hunt
quot;Agile Web Development with Railsquot; Dave Thomas and
David Heinemeier Hansson
quot;Rails Recipesquot; Chad Fowler
many, many more: http://www.rubyonrails.org/books
in Polish:
quot;Programowanie w jezyku Ruby. Wydanie IIquot; Dave Thomas,
˛
Chad Fowler, Andy Hunt
quot;Rails. Przepisyquot; Chad Fowler
quot;Ruby on Rails. Wprowadzeniequot; Bruce A. Tate, Curt Hibbs
´
quot;Ruby on Rails. Cwiczeniaquot; Michał Sobczak



Links

main site: http://www.rubyonrails.org
PL site: http://www.rubyonrails.pl/
general mailing list:
http://groups.google.com/group/rubyonrails-talk
wiki: http://wiki.rubyonrails.org/rails
api: api.rubyonrails.org
74 Quality Ruby on Rails Resources and Tutorials:
http://www.softwaredeveloper.com/features/74-ruby-on-
rails-resources-tutorials-050207/



Events

Rails Conf
Rails Day
local communities & meetings
Ruby on Rails workshops:
http://rubyonrailsworkshops.com/
academic presence


Questions?

pics:
http://www.midcoast.com/ holo/Seth%20in%20Thailand/pages/Rail%20tracks.html,

http://mfrost.typepad.com/cute_overload/2007/05/this_site_is_dr.html

Introduction to Ruby on Rails

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