Introduction to Ruby on Rails

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Agnieszka Figiel

blog.agnessa.eu

Kraków Ruby Users Group

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Ruby on Rails

"Rails is a full-stack framework for developing database-backed web applications according to the Model-View-Control pattern."

www.rubyonrails.org - Ruby on Rails official site

2005 David Heinemeier Hansson

opinionated software:"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."

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Outline

Design Principles MVC architecture Agile Development

Usability and Success Stories Community and Resources

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Design Principles

MVC architecture Agile Development

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Model - View - Controller

separate data (model) from user interface (view)

I Model

I data access and business logic I _{independent of the view and controller} I View

I _{data presentation and user interaction} I read-only access to the model

I Controller

I _{handling events}

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Database Persistance

I OR mapping

Active Record design pattern

I migrations

incremental schema management

I multiple db adapters

MySQL, PostgreSQL, SQLite, SQL Server, IBM DB2, Informix, Oracle, Firebird/Interbase, LDAP, SybaseASA

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Full Stack Framework

I MVC suite

I built-in webserver

I default db adapter

I integrated logger

I AJAX, web services, email

I test framework

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Convention over Configuration

I fixed directory structure

everything has its place – source files, libs, plugins, database files, documentation etc

I file naming conventions

e.g. camel case class name, underscore file name

I database naming conventions

table names, primary and foreign keys

I standard configuration files

e.g. database connections, environment setting definitions (development, production, test)

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DRY - Don’t Repeat Yourself

I reusing code

e.g. view elements

I reusing data

e.g. no need to declare table field names – can be read from the database

I making each line of code work harder

e.g. mini languages for specific domains, like object-relational mapping

I metaprogramming

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Design Principles

MVC architecture

Agile Development

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Model - ActiveRecord

I conventions:

I name based OR mapping: mice db table ->Mouse class I 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 to

manipulate 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’",

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Model - ActiveRecord

I support for basic entity relations (1:1, 1:n, n:n) with

dynamic accessors

backyard_mouse_hole.mice #=> Array of Mouse objects

I parametrised queries against SQL injection, e.g. find all

mice 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 passes

all validation rules, e.g. uniqueness of a given field:

validates_uniqueness_of :login

I object life cycle callbacks, e.g.

before_create, before_save

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View - ActionView

I multiple template types

I oldest and basic: erb (embedded ruby), similar to e.g. jsp I remote javascript templates

I xml templates

I easy reuse of view elements

I _{file inclusion – layouts, templates, partials}

I multiple standard "helpers" – common html element generators (e.g. form elements, paginators)

I ridiculously easy AJAX integration – prototype,

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Controller - ActionController

I all actions grouped logically in controller objects (actions

are public methods of the controller class)

I conventions

I _{name based url – action mapping} e.g. url: myhost.com/mice/show/1

action: ’show’ action in MiceController, params: id=1 I _{name based action - template file mapping}

e.g. action ’show’ in MiceController - template file app/views/mice/show.rhtml

I can be organised in an inheritance hierarchy

reduces code duplication and simplifies code

I action callbacks –

before_filter, after_filter, around_filter

I built-in mechanism of url rewrites – routes

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Design Principles MVC architecture

Agile Development

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Rapid Development

I built-in webserver

I generators – save the fingers

I scaffold – kick-off start

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Debugging

I verbose log output

I breakpoint debugger

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Testing

I test database + fixtures

I unit tests - tests for models

I functional - tests for controllers

I integration - tests for workflow

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Agile Project Heartbeat

I test coverage - rcov

I continuous integration

I iterative db schema control - migrations

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Usability and Success Stories

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Platform Independence

I win, lin, mac

I Apache, Lighttpd, mongrel

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IDEs

I textmate

I vim

I RadRails, Eclipse + RDT, Aptana

I plugins for Idea, NetBeans

I SCiTe

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Scaling

I it scales – a must-see slideshow about scaling twitter (600

req/s!): http://www.slideshare.net/Blaine/scaling-twitter I view caching I _{page caching} I _{action caching} I _{fragment caching} I sql caching I memcached

I shared nothing architecture - multiplying application

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Hosting

I http://wiki.rubyonrails.org/rails/pages/RailsWebHosts

I US - a variety of shared hosting offers

I Poland - poor shared hosting options hosted.pl

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Success Stories

several ror powered high traffic sites

I http://twitter.com/ - community site

I http://www.odeo.com/ - music sharing

I http://www.43things.com/, http://www.43places.com/,

http://www.43people.com/

I 37Signals: BaseCamp, BackPack, Ta-Da List, Writeboard,

CampFire

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Usability and Success Stories

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Books

I in English:

I _{ruby: "Programming Ruby 2nd Edition" (the Pickaxe) Dave} Thomas, with Chad Fowler and Andy Hunt

I _{"Agile Web Development with Rails" Dave Thomas and} David Heinemeier Hansson

I _{"Rails Recipes" Chad Fowler}

I many, many more: http://www.rubyonrails.org/books

I in Polish:

I _{"Programowanie w j ˛ezyku Ruby. Wydanie II" Dave Thomas,} Chad Fowler, Andy Hunt

I _{"Rails. Przepisy" Chad Fowler}

I _{"Ruby on Rails. Wprowadzenie" Bruce A. Tate, Curt Hibbs} I _{"Ruby on Rails. ´}_{Cwiczenia" Michał Sobczak}

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Links

I main site: http://www.rubyonrails.org

I PL site: http://www.rubyonrails.pl/

I general mailing list:

http://groups.google.com/group/rubyonrails-talk

I wiki: http://wiki.rubyonrails.org/rails

I api: api.rubyonrails.org

I 74 Quality Ruby on Rails Resources and Tutorials:

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

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Events

I Rails Conf

I Rails Day

I local communities & meetings

I Ruby on Rails workshops:

http://rubyonrailsworkshops.com/

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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