An Introduction to Ruby

Speaker.new({
:name => "Wes Oldenbeuving",
:twitter => "@Narnach",
:rubyist_since => "Early 2006",
:works_as => "Freelance Rubyist",
:code_at => "github.com/Narnach",
:email => "wes@narnach.com"
})

Overview
What is Ruby?
History and current versions
What does Ruby look like?
Basic tools of the Rubyist
Practical uses of Ruby
The Ruby Community

What is Ruby?

Object oriented

Everything is an object
1.class # => Fixnum
'a'.class # => String
:z.class # => Symbol
class Foo
end
Foo.class # => Class
Foo.new.class # => Foo

Dynamically typed
def foo(bar)
bar * 2
end
foo(1) # => 2
foo("a") # => "aa"

Duck Typing
"a".respond_to? :size # => true
1.respond_to? :+ # => true
1.respond_to? :inject # => false

Scripting language

Everything is an expression

Ruby: the history

Japan

Idea
1993

Productivity and fun

Focus on the programmer,
not the computer

Inspired by
Perl, Smalltalk, Lisp

v0.95
1995

English-language
1999
v1.3

Programming Ruby
2000

Current versions of Ruby

Matz Ruby Interpreter
Stable Ruby 1.8

Yet Another Ruby VM
Development Ruby 1.9

JRuby (1.4)
Ruby 1.8 (1.9) on the JVM

Rubinius
Ruby 1.8 in Ruby
(and a bit of C++)

IronRuby (0.9.2)
Ruby 1.8 without continuations

MacRuby (0.5)
Ruby 1.9 in Objective-C

Maglev
Ruby in Gemstone Smalltalk VM

Ruby: the language

What does Ruby look like?

Strings and Variables
'Hello, Devnology!'
name = 'Devnology' # => "Devnology"
"Hello, #{name}!" # => "Hello, Devnology!"

Methods
str = "Hello, Devnology!"
str.size # => 17
str.sub("Devnology", "World") # => "Hello, World!"
def greet(name="Wes")
"Greetings, #{name}!"
end
puts greet
puts greet('Devnology')
# >> Greetings, Wes!
# >> Greetings, Devnology!

Numbers
1 + 2 # => 3
1 + 2.1 # => 3.1
2**10 # => 1024
9 / 2 # => 4
5 % 3 # => 2
-3.abs # => 3
1.class # => Fixnum
(2**50).class # => Bignum
1.3.class # => Float

Arrays
Array.new # => []
[1,2,3] # => [1, 2, 3]
[1] + [2] << 3 # => [1, 2, 3]
[1,2,3] - [2,3] # => [1]
%w[one two] # => ["one", "two"]
[1,2,3].pop # => 3
[1,2].push(3) # => [1, 2, 3]
[1,2,3].shift # => 1
[2,3].unshift(1) # => [1, 2, 3]
[1,3].insert(1,2) # => [1, 2, 3]

Hashes
options = {:name => "Devnology"}
h = Hash.new # => {}
h['string'] = 1
h[:symbol] = 1
h # => {:symbol=>1, "string"=>1}
h.keys # => [:symbol, "string"]
h[:symbol] # => 1

Iterators
for n in 0..2
puts n
end
(0..2).each do |n|
puts n
end
[0,1,2].each {|n| puts n}

Enumerable
ary = [1,2,3]
ary.map {|n| n * 2} # => [2, 4, 6]
ary.select {|n| n % 2 == 0} # => [2]
ary.inject(0) {|sum, n| sum + n} # => 6

Control structures
if some_condition
# ...
elsif other_condition
# ...
else
# ...
end
while condition
# ...
end
puts "lol" if funny?

Regular Expressions
str = "Hello, world!"
str.gsub(/[aeiou]/,"*") # => "H*ll*, w*rld!"
str =~ /w(or)ld/ # => 7
$1 # => "or"
match = str.match(/w(or)ld/) # => #<MatchData:
0x532cbc>
match[0] # => "world"
match[1] # => "or"

Error handling
begin
raise "Standard error"
rescue => e
p e
end
# >> #<RuntimeError: Standard error>
begin
raise StandardError.new("Oh, oh")
rescue RuntimeError
puts "runtime"
rescue StandardError
puts "standard"
end
# >> standard

System interaction
system "ls"
output = `ls`
ARGV
File.open('test.txt','w') do |file|
file.write("linen")
file.puts("line")
end
File.read('test.txt')

Classes
class Calc
attr_accessor :factor
def initialize(factor=2)
@factor = factor
end
def multiply(value)
@factor * value
end
end
calc = Calc.new
calc.multiply 5 # => 10
calc.factor = 3
calc.multiply 5 # => 15

Inheritance
class Foo
def greet
"Hi, #{value}"
end
def value
"foo"
end
end
class Bar < Foo
def value
"bar"
end
end
Foo.new.greet # => "Hi, foo"
Bar.new.greet # => "Hi, bar"

Mixins & Open Classes
module Even
def even?
self % 2 == 0
end
end
class Fixnum
include Even
end
1.even? # => false
2.even? # => true

Class methods
class Foo
def self.bar
"BAR!"
end
def bar
"bar"
end
end
Foo.bar # => "BAR!"
Foo.new.bar # => "bar"

Basic tools of a Rubyist

Rubygems

Rdoc

Interactive Ruby

Practical uses of Ruby

Ruby on Rails
class BlogPost < ActiveRecord::Base
belongs_to :user
has_many :comments
validates_presence_of :user_id
validates_associated :user
validates_length_of :title, :within => 10..100
validates_length_of :body, :within => 100..5000
end
BlogPost.new(:title => "Hello", :body => "foo!")

Rspec
it "should be awesome" do
foobar = FooBar.new
foobar.should be_awesome
end

Cucumber
Feature: Write blog post
As a blogger
I want to create a new blog post
So that I can share my knowledge
Scenario: Click the Add group button
Given I am on the homepage
When I follow "New post"
Then I should be on the new blog post page
Given /^I am on (.+)$/ do |page_name|
visit path_to(page_name)
end

Scripting / automation

DSL: Rake
desc "Clean everything up"
task :cleanup do
Cleaner.cleanup!
end
desc "Make sure everything is shiny"
task :shiny => :cleanup do
Shiner.polish!
end

DSL: Capistrano
set :application, "blog"
set :repository, "git@github.com:Narnach/#{application}.git"
set :deploy_to, "/var/www/www.#{application}.com"
set :scm, :git
role :web, "server"
role :app, "server"
role :db, "server", :primary => true
namespace :deploy do
desc "Restart Passenger"
task :restart, :roles => :app, :except => { :no_release => true } do
run "touch #{File.join(current_path,'tmp','restart.txt')}"
end
end

The Ruby Community

Rubyists

Amsterdam.rb
Monthly beer night
Presentation nights

Utrecht.rb
Monthly beer night

rubyists.eu

ruby-groups.org
dev-groups.org