Ruby Intro

• Japan,
1993

• Perl,
Smalltalk,
Lisp

• Readability,
writability

• English
language,
1999

• Windows,
Linux,
Mac
OS
X

• Included
with
Apple
developer
tools

• “Everything
is
an
object.”
• Except
for
primiNves.
But
you
can
box
those.
• Arrays
are
special.
• Classes
are
a
liQle
special,
too.

• “Everything
is
an
object.”
• Period.

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 do_stuff(thing)
thing.do_the_stuff
end

class TheThing
def do_the_stuff
puts "Stuff was done!"
end
end

do_stuff(TheThing.new)

Dynamically
typed
t = TheThing.new
t.respond_to? :do_the_stuff # => true

def do_stuff(thing)
if thing.respond_to? :do_the_stuff
thing.do_the_stuff
else
raise "What on earth is this?"
end
end

Strings
&
variables

name = 'World' # => "World"

"Hello, #{name}" # => "Hello, World"

'Hello, #{name}' # => "Hello, #{name}"

Every
expression
has
a
value

def say_it_isnt_so(really = false)
if really
"All's fine!"
else
"All your base are belong to us."
end
end

say_it_isnt_so # => "All your base
are belong to us."
say_it_isnt_so true # => "All's fine!"

Return

def do_complicated_stuff(take_shortcut)
if take_shortcut
return 42
end
do_really_complicated_stuff
end

Numbers

1 + 1 # => 2
1 + 1.1 # => 2.1
6 * 7 # => 42
6 ** 7 # => 279936

Math.sqrt(65536) # => 256.0

1.class # => Fixnum
(2 ** 42).class # => Fixnum
(2 ** 64).class # => Bignum

1.1.class # => Float

Arrays

Array.new # => []
Array.new(3) # => [nil, nil, nil]
[] # => []

a = [1,2,3] # => [1, 2, 3]
a[0] = 'one' # => "one"
a # => ["one", 2, 3]
a[-1] # => 3
a[1..2] # => [2, 3]

Arrays
a = [1,2,3] # => [1, 2, 3]

a.push 4 # => ["one", 2, 3, 4]
a.pop # => 4
a # => ["one", 2, 3]

[1,2,3] | [2, 4] # => [1, 2, 3, 4]
[1,2,3] & [2, 4] # => [2]

Hashes

Hash.new # => {}
{} # => {}

h = {1 => "one", 2 => "two"}
h[1] # => "one"
h["1"] # => nil

h[:one] = "einz" # => "einz"
h[:one] # => "einz"

h.keys # => [1, 2, :one]
h.values # => ["one", "two", "einz"]

Fun
with
arrays
&
hashes

def do_stuff(options = {})
puts options[:hello] if options.include?(:hello)
end

do_stuff
# => nil
do_stuff :hello => "hi"
# hi
# => nil

Fun
with
arrays
&
hashes

[1,2,3,5,7].select {|x| x.even?}
# => [2]

[1,2,3,5,7].inject(1) { |x, n| n * x}
# => 210

[1,2,3,5,7].map { |n| n * n }
# => [1, 4, 9, 25, 49]

{1 => "one", 2 => "two"}.map { |k,v| v }
# => ["one", "two"]

Control
structures

if condition
# ...
elsif other_condition
# ...
end

unless condition
# ...
end

while
# ...
end

Control
structures

case (1024)
when 42 then puts "my favorite number"
when 2 then puts "my second favorite number"
when 1024, 2048 then puts "fair enough"
else "this number sucks"
end

Control
structures

puts "How are you gentlemen!!" if role.cats?

puts "mommy!" while reaction_from_mommy.nil?

class Pet Classes
attr_accessor :name

def initialize(name)
@name = name
end

def sit!
puts "Wuff"
end
end

fido = Pet.new("fido") # => #<Pet:0x10116e908
@name="fido">
fido.name # => "fido"
fido.sit! # => "Wuff"

Classes

class Cat < Pet
def sit!
if rand(10) > 8 # decide our mood
super
else
puts "No way!"
end
end
end

mimi = Cat.new("mimi") # => #<Cat:0x101131d00
@name="mimi">
mimi.sit! # => "No way!"

Classes
class Cat
def self.purr
puts "Huh, what? I'm the class!"
end

def purr
puts "prrrrrrr"
end
end

Cat.purr
# "Huh, what? I'm the class!"
Cat.new("mimi").purr
# prrrrrrr

Classes

class Fixnum
def even?
return false if eql? 2
super
end
end

2.even? # => false
4.even? # => true

Modules
module ThingsDoer
def do_one_thing
puts "doing one thing"
end
end

ThingsDoer::do_one_thing
# "doing one thing"

# Modules can be used to group methods,
classes or other modules

Modules

class Pet
include ThingsDoer
end

# we had a Pet instance of fido

fido.do_one_thing
# "doing one thing"

Naming
convenDons

CamelCased # Classes, modules
with_underscores # methods, local variables

@instance_variable
@@class_variable
$GLOBAL_VARIABLE

Code
blocks
[1,2,3,5,7].select {|x| x.even?}
# => [2]

def do_random_nr_of_times &block
nr = rand(10)
for i in 1..nr
yield
end
end

do_random_nr_of_times { puts "bla" }
# bla
# bla
# bla
# => 1..3

Code
blocks

def run
value = "bla"
do_random_nr_of_times { puts value }
end
run
# bla
# bla
# => 1..2

Code
blocks
the_time = Time.now
# Sun Nov 29 20:15:47 0100 2009
the_time
# Sun Nov 29 20:15:47 0100 2009
the_time
# Sun Nov 29 20:15:47 0100 2009

>> the_time = lambda { Time.now }
# => #<Proc:0x0000000100567178@(irb):463>
the_time.call
# Sun Nov 29 20:18:16 0100 2009
the_time.call
# Sun Nov 29 20:18:20 0100 2009

OpDonal
language
elements

def my_method(data, options = {})
# ...
end

# Full signature
my_method("bla", {:option => 'value', :two => 2})
# The last parameter a hash? implicit.
my_method("bla", :option => 'value', :two => 2)
# Parentheses are optional
my_method "bla", :option => 'value', :two => 2

# As long as its unambiguous, it's OK

Regular
expressions

s = "Ruby rules"
# => "Ruby rules"
s =~ /rules/
# => 5
s.gsub(/es/, "ez")
# => "Ruby rulez"
s.gsub(/[aeiou]/, "*")
# => "R*by r*l*s"
m = s.match(/([aeiou][^aeiou])/)
# => #<MatchData "ub" 1:"ub">
m[0]
# => "ub"

ExcepDons
begin
raise "Someone set us up the bomb."
rescue => e
puts e.inspect
end
# <RuntimeError: Someone set us up the bomb.>

begin
raise StandardError.new("For great justice.")
rescue StandardError
puts "standard"
rescue RuntimeError
puts "runtime"
end
# standard

What’s
more?

• No
threading
(at
least,
by
default)
• Only
false
and
nil
are
not
true
def my_method(my_object)
puts my_object && my_object.to_s
end
my_method(1) # => 1
my_method(nil) # => nil

h[:bla] ||= "bla"

What
haven’t
I
talked
about?

• TesNng
• RSpec
• DocumentaNon
• RDoc

What
haven’t
I
talked
about?

• Gems
• Like
‘apt’
for
ruby
• Deployment
• SVN
• Capistrano

What
haven’t
I
talked
about?
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 -> "My first blog", :body => "is
way too short.")

What
haven’t
I
talked
about?

• Ruby
on
Rails
• Web
framework
• Strict
MVC
separaNon
• Handles
persistence
http://pragprog.com/
titles/rails2

module Ruby
include(DynamicLanguage)
include(ObjectOriented)
include(DuckTyping)

def ruby
@everything_is_an_object = true
end

def language
{"hashes" => :awesome, "array" => :awesome}
value = 'supported'
"String variable substibution is #{value}"
end

def tools
{:editor => 'Textmate',
:runtime => 'included in OS X'}
end
end

thank_audience
:speaker => 'Angelo vd Sijpt',
:greeting => 'You were awesome!',
:find_more_at ['ruby-lang.org',
'rubyists.eu']

Ruby Intro

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