Rochester on Rails: Introduction to Ruby

RubyProgrammers’ Best Friend

Jason Morrison

January 19, 2006

Rochester on Rails

History

RubyYukihiro “Matz” Matsumoto

February 24, 1993

Perl Java Python Ruby PHP1987 1991 1993 1995

Examples!

5.times { print “Ruby! " }

Ruby! Ruby! Ruby! Ruby! Ruby!

5.times { print “Ruby! " }

[‘one’,‘two’,‘three’].each {|num| puts num.capitalize}

[‘one’,‘two’,‘three’].each {|num| puts num.capitalize}

OneTwoThree

Everything isan object

-21474836480.abs

-21474836480.abs21474836480

“Rats live on no evil star”

.reverse.capitalize

“Rats live on no evil star”

.reverse.capitalize

“Rats live on no evil star”

3.hours.from_now

3.hours.from_now

Thu Jan 19 22:05:00 Eastern Standard Time 2006

Conventions

Variables

colored_index_cards

Class Names

DromedaryDiner

Symbols

:creme_de_menthe

Instance Variables

@euros_per_liter

Constants

Kilograms_Per_Pound

Syntax

Methods

def say_hello(name) result = “Hello, #{name}!” return resultend

puts say_hello(“world”)

Methods

def say_hello(name) “Hello, #{name}!”end

puts say_hello(“world”)

Classesclass MathWhiz

def say_square(value) puts value * value

end

end

sam = MathWhiz.new

sam.say_square(5)

Open Classesclass Integer

def squared

self * self

end

end

5.squared #=> 25

Inheritance

class Whopper < Burger @maker = “Burger King” @calories = 0.67 * 10**3end

Class Methods

class FileUtil def self.mkdir(dir) # do it! endend

FileUtil.mkdir(“oranges”)

Modules

module Trig PI = 3.141592654 def Trig.sin(x) # .. end def Trig.cos(x) # .. endend

Modules

require "trig"y = Trig.sin(Trig::PI/4)0.707106780551956

Mixins

module Debug def whoAmI? “#{self.type.name} ” + “(\##{self.id}): ” + “#{self.to_s}" endend

Mixins

class Phonograph include Debug # ...endph = Phonograph.new("West End Blues")ph.whoAmI?"Phonograph (#537766170): West End Blues"

Attributes

class PlainOldRubyObject attr_accessor :food, :drinks attr_reader :advice attr_writer :write_onlyend

Scopeclass Poet #public by default def poetry end

protected def family_legacy end

private def hopes_and_dreams endend

Arrays

foo = []

foo << 1 #=> [1]foo << 2 #=> [1, 2]foo << 3 #=> [1, 2, 3]

bar = [1, 2, 3]

bar << 4 #=> [1, 2, 3, 4]bar << 5 #=> [1, 2, 3, 4, 5]bar << 6 #=> [1, 2, 3, 4, 5, 6]

folks = %w( Charles Ed Amanda )#=> [“Charles”, “Ed”, “Amanda”]

folks[1]Ed

Hashes

menu = { :douglas_sirk_steak => 17.50, :vanilla_coke => 2.75, :durwood_kirby_burger => 9.75, :five_dollar_shake => 5.00}

menu[:vanilla_coke]2.75

Flow

if ( score >= 5000 ) puts “You win!”elsif ( score <= 0 ) puts “Game over.”else puts “Current score: #{score}”end

puts “Watch out!” if lion_distance < 5

Blocks

1.upto(5) { |x| puts x }

12345

5.downto(1) do |time| print “#{time}... ” puts “!” if time <= 3end

5... 4... 3... !2... !1... !

Fín!

Homepagewww.ruby-lang.org

Try Ruby in your browsertryruby.hobix.com

Ruby with humor www.poignantguide.net