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An Introduction to Ruby and Rails
Matthew BohnsackWannabe RubyistNovember 9th 2005
An Introduction to Ruby and Rails 2November 9th 2005
Outline
What is Ruby and why should I care? What is Rails and why should I care? Two must-have tools for Ruby development Major Ruby features (the language in a nutshell) Rails overview Where to go for more information Questions / Hacking
An Introduction to Ruby and Rails 3November 9th 2005
What is Ruby? Why should I care?
What: The Wikipedia answer is here. Created/lead by Matz (Japanese) Open Source interpreted scripting language, like Perl, Python,
Tcl, etc., but focused on being very object oriented, expressive, and bringing joy to programming.
Principle of least surprise Why:
Productivity ideas presented in Ousterhout’s 1998 paper coming to very serious critical mass (and beyond)
Learn a new language to learn new ways of thinking about code in any language (e.g., blocks and iterators)
Joy!
An Introduction to Ruby and Rails 4November 9th 2005
What is Rails? Why should I care?
What: Web Framework that makes building database-driven MVC-oriented web apps
easy through a template engine, ORM (ActiveRecord) and other best practices, such as test driven development, deployment tools, patterns, etc.
Much less complicated than J2EE solutions, but perhaps more so than PHP or Perl in cgi-bin.
Copy cats are being created in other languages: Python (TurboGears) Perl (Maypole)
http://rubyonrails.org/ + book + online screencasts + online docs & tutorials Why:
I’ve been watching the world of web development since ~ 1995, and I’ve never seen anything like Rails in terms of buzz, momentum, adoption rate, etc.
An Introduction to Ruby and Rails 5November 9th 2005
Must have tool #1: irb
Interactive ruby console:Experiment on the flyTab complete object methods…
# ~/.irbrc
require 'irb/completion'
use_readline=true
auto_indent_mode=true
An Introduction to Ruby and Rails 6November 9th 2005
Must have tool #2: ri
Console-based Ruby doc tool
An Introduction to Ruby and Rails 7November 9th 2005
Ruby in a nutshell – irb sessions follow Like all interpreted scripting languages, you can
put code into a file, chmod +x, then just execute it.
But, we’ll mostly use irb sessions in this presentation…
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Ruby in a nutshell – objects are everywhere Some languages have built-in types that aren’t
objects. Not so with Ruby. Everything’s an object:
An Introduction to Ruby and Rails 9November 9th 2005
Ruby in a nutshell – objects have methods
Bang on the tab key in irb to see the methods that are available for each object.
An Introduction to Ruby and Rails 10November 9th 2005
Ruby in a nutshell – Variables Local variables - start with lower case:
foo bar
Global variables - start with dollar sign: $foo $bar
Constants and Classes – start with capital letter: CONSTANT Class
Instance variables – start with at sign: @foo @bar
Class variables – start with double at sign: @@foo @@bar
An Introduction to Ruby and Rails 11November 9th 2005
Ruby in a nutshell – Arrays
An Introduction to Ruby and Rails 12November 9th 2005
Ruby in a nutshell – Hashes
An Introduction to Ruby and Rails 13November 9th 2005
Ruby in a nutshell – Symbols Starts with a ‘:’ Only one copy of a symbol kept in memory
An Introduction to Ruby and Rails 14November 9th 2005
Ruby in a nutshell – Blocks & Iterators
An Introduction to Ruby and Rails 15November 9th 2005
Ruby in a nutshell – It’s easy to build classes
An Introduction to Ruby and Rails 16November 9th 2005
Ruby in a nutshell – It’s fun to play with classes (like the one we just made)
An Introduction to Ruby and Rails 17November 9th 2005
Ruby in a nutshell – Classes are open
Example shown here uses our Hacker class, but what happens when the whole language is open?
An Introduction to Ruby and Rails 18November 9th 2005
Ruby in a nutshell – Other notes on Classes Ruby only has single inheritance. This
makes things simpler, but mix-ins provide much of multiple inheritance’s benefit, without the hassle.
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Ruby in a nutshell – a few gotchas
Despite the principle of least surprise: Zero isn’t false:
No increment operator (foo++). Instead use: foo += 1 foo = foo + 1
An Introduction to Ruby and Rails 20November 9th 2005
Ruby in a nutshell – RubyGems
CPAN for Ruby? http://docs.rubygems.org/ Examples:
gem list
gem install redcloth --version ">= 3.0.0" …
Using gems in your program: require ‘rubygems’ require ‘some_gem’
An Introduction to Ruby and Rails 21November 9th 2005
Want to learn more Ruby? Excellent, simple, beginner’s tutorial:
http://www.math.umd.edu/~dcarrera/ruby/0.3/index.html Other stuff at end of talk Start hacking
An Introduction to Ruby and Rails 22November 9th 2005
Quick Rails Demo – Build a TODO list application in 5 minutes Define database rails todo cd todo Edit config/database.yml ./script/generate model Todo ./script/generate scaffold todo Look at scaffolding ./script/server –b www.bohnsack.com Add due_date field, regenerate scaffolding, and check the results ./script/console
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Where to go for more information Books:
Online material: First edition of Pickaxe online for free http://www.ruby-doc.org/ why’s (poignant) guide to Ruby http://rubyonrails.org/ Rails screencast(s) Planet Ruby on Rails
An Introduction to Ruby and Rails 24November 9th 2005
The End / Questions