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

The language

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"

Textmate

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']

http://changelos.com	21
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Ruby Intro

by Angelo van der Sijpt on Dec 01, 2009

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Ruby Intro — Presentation Transcript