An introduction to Ruby

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

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

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

http://www.techgig.com	41
http://devnology.nl	4
http://www.slideshare.net	3

An introduction to Ruby

by Wes Oldenbeuving on Nov 08, 2009

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An introduction to Ruby — Presentation Transcript