An Introduction to Ruby and Rails

Matthew BohnsackWannabe RubyistNovember 9th 2005

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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

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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!

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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.

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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

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Must have tool #2: ri

Console-based Ruby doc tool

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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:

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Ruby in a nutshell – objects have methods

Bang on the tab key in irb to see the methods that are available for each object.

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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

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Ruby in a nutshell – Arrays

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Ruby in a nutshell – Hashes

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Ruby in a nutshell – Symbols Starts with a ‘:’ Only one copy of a symbol kept in memory

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Ruby in a nutshell – Blocks & Iterators

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Ruby in a nutshell – It’s easy to build classes

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Ruby in a nutshell – It’s fun to play with classes (like the one we just made)

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Ruby in a nutshell – Classes are open

Example shown here uses our Hacker class, but what happens when the whole language is open?

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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

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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’

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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

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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

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The End / Questions