Introduction to Ruby on Rails

Introduction to Ruby on Rails

Agnieszka Figielblog.agnessa.eu

Kraków Ruby Users GroupMay 19th 2007

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

Ruby on Rails

"Rails is a full-stack framework for developingdatabase-backed web applications according to theModel-View-Control pattern."www.rubyonrails.org - Ruby on Rails official site

2005 David Heinemeier Hansson

opinionated software: "it’s a very pragmatic, very targetedframework with a strong sense of direction. You might notshare its vision, but it undeniably has one."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





Model - View - Controller

separate data (model) from user interface (view)

I ModelI data access and business logicI independent of the view and controller

I ViewI data presentation and user interactionI read-only access to the model

I ControllerI handling eventsI operating on model and view



Database Persistance

I OR mappingActive Record design pattern

I migrationsincremental schema management

I multiple db adaptersMySQL, PostgreSQL, SQLite, SQL Server, IBM DB2,Informix, Oracle, Firebird/Interbase, LDAP, SybaseASA



Full Stack Framework

I MVC suiteI built-in webserverI default db adapterI integrated loggerI AJAX, web services, emailI test frameworkI plugins



Convention over Configuration

I fixed directory structureeverything has its place – source files, libs, plugins,database files, documentation etc

I file naming conventionse.g. camel case class name, underscore file name

I database naming conventionstable names, primary and foreign keys

I standard configuration filese.g. database connections, environment setting definitions(development, production, test)



DRY - Don’t Repeat Yourself

I reusing codee.g. view elements

I reusing datae.g. no need to declare table field names – can be readfrom the database

I making each line of code work hardere.g. mini languages for specific domains, likeobject-relational mapping

I metaprogrammingdynamically created methods



Design Principles

MVC architecture

Agile Development





Model - ActiveRecord

I conventions:I name based OR mapping: mice db table -> Mouse classI primary key: auto-incremented numeric field called "id"I foreign key: "[singular_of_foreign_table_name]_id", e.g.

"cat_id"I dynamic getters, setters, finders

dynamic means the existance of a field in db is enough tomanipulate it, e.g. dynamic getter like: mouse.name

I abstracted db operations - create, update, destroy, find, ...possible to use raw sql, but usually unnecessary, e.g.:

Mouse.find(:all, :include => {:mouse_holes},:conditions => "location = ’shed’",:order => "name", :limit => 10)



Model - ActiveRecord

I support for basic entity relations (1:1, 1:n, n:n) withdynamic accessorsbackyard_mouse_hole.mice #=> Array of Mouse objects

I parametrised queries against SQL injection, e.g. find allmice whose name is sth entered by the user:

Mouse.find(:all, :conditions => ["name = ?",mouse_name)

I validators: an object won’t be saved in db unless it passesall validation rules, e.g. uniqueness of a given field:validates_uniqueness_of :login

I object life cycle callbacks, e.g.before_create, before_save

I Single Table Inheritance, polymorphic associations



View - ActionView

I multiple template typesI oldest and basic: erb (embedded ruby), similar to e.g. jspI remote javascript templatesI xml templates

I easy reuse of view elementsI file inclusion – layouts, templates, partialsI multiple standard "helpers" – common html element

generators (e.g. form elements, paginators)

I ridiculously easy AJAX integration – prototype,scriptaculous



Controller - ActionController

I all actions grouped logically in controller objects (actionsare public methods of the controller class)

I conventionsI name based url – action mapping

e.g. url: myhost.com/mice/show/1action: ’show’ action in MiceController, params: id=1

I name based action - template file mappinge.g. action ’show’ in MiceController - template fileapp/views/mice/show.rhtml

I can be organised in an inheritance hierarchyreduces code duplication and simplifies code

I action callbacks –before_filter, after_filter, around_filter

I built-in mechanism of url rewrites – routesI easy access to request data, session, cookies



Design Principles

MVC architecture

Agile Development





Rapid Development

I built-in webserverI generators – save the fingersI scaffold – kick-off startI plugins, libraries, tons of contributed code



Debugging

I verbose log outputI breakpoint debuggerI script/console



Testing

I test database + fixturesI unit tests - tests for modelsI functional - tests for controllersI integration - tests for workflowI testing directly in browser - Selenium



Agile Project Heartbeat

I test coverage - rcovI continuous integrationI iterative db schema control - migrationsI automated deployment - capistrano



Design Principles

MVC architecture

Agile Development





Platform Independence

I win, lin, macI Apache, Lighttpd, mongrelI gem package manager



IDEs

I textmateI vimI RadRails, Eclipse + RDT, AptanaI plugins for Idea, NetBeansI SCiTeI jEdit



Scaling

I it scales – a must-see slideshow about scaling twitter (600req/s!): http://www.slideshare.net/Blaine/scaling-twitter

I view cachingI page cachingI action cachingI fragment caching

I sql cachingI memcached

I shared nothing architecture - multiplying applicationservers



Hosting

I http://wiki.rubyonrails.org/rails/pages/RailsWebHostsI US - a variety of shared hosting offersI Poland - poor shared hosting options hosted.plI Root VPS



Success Stories

several ror powered high traffic sitesI http://twitter.com/ - community siteI http://www.odeo.com/ - music sharingI http://www.43things.com/, http://www.43places.com/,

http://www.43people.com/I 37Signals: BaseCamp, BackPack, Ta-Da List, Writeboard,

CampFireI http://www.strongspace.com/ - storing and sharing files



Design Principles

MVC architecture

Agile Development





Books

I in English:I ruby: "Programming Ruby 2nd Edition" (the Pickaxe) Dave

Thomas, with Chad Fowler and Andy HuntI "Agile Web Development with Rails" Dave Thomas and

David Heinemeier HanssonI "Rails Recipes" Chad FowlerI many, many more: http://www.rubyonrails.org/books

I in Polish:I "Programowanie w jezyku Ruby. Wydanie II" Dave Thomas,

Chad Fowler, Andy HuntI "Rails. Przepisy" Chad FowlerI "Ruby on Rails. Wprowadzenie" Bruce A. Tate, Curt HibbsI "Ruby on Rails. Cwiczenia" Michał Sobczak



Links

I main site: http://www.rubyonrails.orgI PL site: http://www.rubyonrails.pl/I general mailing list:

http://groups.google.com/group/rubyonrails-talkI wiki: http://wiki.rubyonrails.org/railsI api: api.rubyonrails.orgI 74 Quality Ruby on Rails Resources and Tutorials:

http://www.softwaredeveloper.com/features/74-ruby-on-rails-resources-tutorials-050207/



Events

I Rails ConfI Rails DayI local communities & meetingsI Ruby on Rails workshops:

http://rubyonrailsworkshops.com/I 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

Technology

Introduction to Ruby on Rails