FossConf'08
Ruby – An Introduction
T.Shrinivasan
tshrinivasan@gmail.com
Indian Linux User Group, Chennai

Ruby is a Programming Language

There are so many
Programming Languages.
Why Ruby?

Ruby is simple and beautiful

Ruby is Easy to Learn

Ruby is Free Open Source Software

Ruby on Rails – Web Framework

RAA
● Ruby Application Archive
● 1648 projects
● http://raa.ruby-lang.org

Rubyforge
● 5070 projects and libraries
● http://rubyforge.org/

Can do
●
Text Handling ●
Games
●
System Administration ●
NLP
●
GUI programming
●
Web Applications ●
...
●
Database Apps
●
Scientific Applications

History

Ruby
Yukihiro “Matz” Matsumoto
Japan
February 24, 1993

Perl Java Python Ruby PHP
1987 1991 1993 1995

What is Ruby?

Ruby is…
A dynamic, open source
programming language with a focus on
simplicity and productivity. It has an
elegant syntax that is natural to read
and easy to write.

Quick and Easy
●
Intrepreted Scripting Language
●
Variable declarations are unnecessary
●
Variables are not typed
●
syntax is simple and consistent
●
memory management is automatic

Object Oriented Programming
●
Everything is an object
●
classes, methods, inheritance, etc.
●
singleton methods
●
\"mixin\" functionality by module
●
iterators and closures

Examples!

5.times { print “Ruby! \" }

5.times { print “Ruby! \" }
Ruby! Ruby! Ruby! Ruby! Ruby!

Everything is
an object

100.next

100.next
101

“I love Ruby” 
.reverse.capitalize

“I love Ruby” 
.reverse.capitalize
“Ybur evol i”

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
Person

Symbols
:street_name

Instance Variables
@school_name

Constants
Kilograms_Per_Pound

Input

puts “What is Your name?”
name = gets
name = name.chomp
puts \"Hello\" + name + \" .Welcome\"

Flow

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

puts “PASS” if mark > 35

Loop

count = 0
5.times do
count += 1
puts \"Count =\" + count.to_s
end

Count = 1
Count = 2
Count = 3
Count = 4
Count = 5

count = 0
while count < 10
puts \"Count = \" +count.to_s
count += 1
end

Blocks

1.upto(5) { |x| puts x }
1
2
3
4
5

5.downto(1) do |time|
print “#{time}... ”
puts “!” if time <= 3
end
5... 4... 3... !
2... !
1... !

Array

Array
numbers = [ \"zero\", \"one\", \"two\",
\"three\", \"four\" ]

Array
numbers = [ \"zero\", \"one\", \"two\",
\"three\", \"four\" ]
>> numbers[0]
=> \"zero\"
>> numbers[4]
=> \"four\"

Array
numbers = [ \"zero\", \"one\", \"two\",
\"three\", \"four\" ]
>> numbers[3].upcase
=> \"THREE\"
>> numbers[3].reverse
=> \"eerht\"

Sort Array
primes = [ 11, 5, 7, 2, 13, 3 ]

Sort Array
primes = [ 11, 5, 7, 2, 13, 3 ]
primes.sort

Sort Array
primes = [ 11, 5, 7, 2, 13, 3 ]
primes.sort
=> [2, 3, 5, 7, 11, 13]

Sort Array
names = [ \"Shrini\", \"Bala\",
\"Suresh\", \"Arul\"]

Sort Array
names = [ \"Shrini\", \"Bala\",
\"Suresh\", \"Arul\"]
names.sort

Sort Array
names = [ \"Shrini\", \"Bala\",
\"Suresh\", \"Arul\"]
names.sort
=>[\"Arul\", \"Bala\", \"Shrini\",
\"Suresh\"]

More on Arrays
●
Reverse
●
Length
●
Delete
●
Join
●
Find
●
More than 100 methods

Hashes

menu = {
:idly => 2.50,
:dosai => 10.00,
:coffee => 5.00,
:ice_cream => 5.00
}
menu[:idly]
2.50

Methods

Methods
def say_hello(name)
result = “Hello, #{name}!”
return result
end
puts say_hello(“world”)

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

Class

Classes
class MathWhiz
def say_square(value)
puts value * value
end
end
sam = MathWhiz.new
sam.say_square(5)

Inheritance
class Dog < Animal
@catagory = “mammal”
@legs = 4
end

Module

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

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

Attributes
class PlainOldRubyObject
attr_accessor :food, :drinks
attr_reader :advice
attr_writer :write_only
end

Scope
class Poet
#public by default
def poetry
end
protected
def family_legacy
end
private
def hopes_and_dreams
end
end

THE END
of code :-)

How to Learn?

irb
● interactive ruby
● A ruby Shell
● Instance response
● learn as you type

Web sites
Web Sites

http://ruby­lang.org
www.ruby­lang.org

www.rubyforge.net

http://www.ruby­forum.com/

Training Centers

Ruby User Groups
chennairb@googlegroups.com
● Mailing List
● Meetings
● Tutorial Sessions
Join Today

We thank and for Photos
Copyright (c) 2008
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.2
or any later version published by the Free Software Foundation.
http://www.gnu.org/copyleft/fdl.html