1. Ruby Talk – An Introduction to
Premshree Pillai
premshree@livejournal.com

2. Scope of Talk
What this talk is and what it isn’t
Me, myself
What is?
Why use?
How to? (a quick run through the syntax)
Quick comparisons (with Perl and Python)
Resources
Ruby Talk - An Introduction to Ruby -- Linux Bangalore/2004 2

3. Purpose
What this talk is?
Get you interested
Get you started with Ruby
What it isn’t?
Not a tutorial
Ruby Talk - An Introduction to Ruby -- Linux Bangalore/2004 3

4. Who am I?
(or why should you listen to me)
21/male/single :)
Technology consultant
Freelance writer since 2001
Perl/Python/Ruby/REBOL hacker
Ruby Talk - An Introduction to Ruby -- Linux Bangalore/2004 4

5. History (Ruby’s, not mine)
Created (in Japan) by Yukihiro
Matsumoto, popularly called Matz
Named as “Ruby” to reflect its Perl
hertitage
Released to the public in 1995
Licensed under GPL or Ruby terms
Ruby Talk - An Introduction to Ruby -- Linux Bangalore/2004 5

6. What the heck is Ruby?
An object-oriented “scripting” language
As powerful as Perl; simpler, better OO
The simplicity of Python
Follows the principle of “Least
Surprise” – What You Expect Is What
You Get
Ruby Talk - An Introduction to Ruby -- Linux Bangalore/2004 6

7. Where can you use Ruby?
System (n/w, RegExps)
Web programming (using CGI)
 Agents, crawlers
DB programming (using DBI)
GUI (Tk, RubyMagick)
Ruby Talk - An Introduction to Ruby -- Linux Bangalore/2004 7

8. General Features
High level language
True OO (everything’s an object!)
Interpreted
Portable
Low learning curve
A quick scan thro’ the syntax
Ruby Talk - An Introduction to Ruby -- Linux Bangalore/2004 8

9. Running Ruby
From the command line:
ruby file.rb
Windows binary comes bundled with
Scintilla
Ruby Talk - An Introduction to Ruby -- Linux Bangalore/2004 9

10. Basic stuff
print 'Hello, world!'
p 'Hello, world!' # prints with
newline
my_var = gets # get input
Ruby Talk - An Introduction to Ruby -- Linux Bangalore/2004 10

11. Operators
(addition)
+
- (subtraction/negation)
* (multiplication)
/ (division)
% (modulus)
** (exponentiation)
Ruby Talk - An Introduction to Ruby -- Linux Bangalore/2004 11

12. Operators (contd.)
==
<=> (returns -1, 0 or 1)
<, <=, >=, >
=~ (matching)
eql? (test of equality of type and
values)
Ruby Talk - An Introduction to Ruby -- Linux Bangalore/2004 12

13. Operators (contd.)
++ and -- are not reserved operators
Use += and +-
Ruby Talk - An Introduction to Ruby -- Linux Bangalore/2004 13

14. Logical Operators
and
or
not
Ruby Talk - An Introduction to Ruby -- Linux Bangalore/2004 14

15. Typing
Dynamic typed
 Type checking at run-time
Strong typed
Ruby Talk - An Introduction to Ruby -- Linux Bangalore/2004 15

16. Basic Data Types
Integers and floats
Strings
Ranges
Arrays
Hashes
Ruby Talk - An Introduction to Ruby -- Linux Bangalore/2004 16

17. Strings
my_str = 'whatever'
my_str = quot;blah, blahquot;
my_str.split(quot;,quot;)[0].split(quot;quot;)[2] * 3
Ruby Talk - An Introduction to Ruby -- Linux Bangalore/2004 17

18. Ranges
Inclusive range
my_range = 1 .. 3
my_range = 'abc' .. 'abf'
Non-inclusive range
my_range = 1 … 5
my_range = 'abc' … 'abf'
Ruby Talk - An Introduction to Ruby -- Linux Bangalore/2004 18

19. Arrays
my_array = [1, 2, 3]
Common methods:
my_array.length
my_array << 4
my_array[0], etc.
Ruby Talk - An Introduction to Ruby -- Linux Bangalore/2004 19

20. Hashes
my_hash = {
'desc' => {'color' => 'blue',},
1 => [1, 2, 3]
}
print my_hash['desc']['color']
will return
blue
Ruby Talk - An Introduction to Ruby -- Linux Bangalore/2004 20

21. Hashes (contd.)
Common methods:
my_hash.keys
my_hash.values
Ruby Talk - An Introduction to Ruby -- Linux Bangalore/2004 21

22. Data Type Conversion
Converting to an Array:
var_data_type.to_a
Converting to an String:
var_data_type.to_s
More (guess!):
var_data_type.to_i
var_data_type.to_f
Ruby Talk - An Introduction to Ruby -- Linux Bangalore/2004 22

23. Everything's an Object
Methods can be applied to data
directly – not just on variables holding
data
Example:
5.to_s will return quot;5quot;
Ruby Talk - An Introduction to Ruby -- Linux Bangalore/2004 23

24. Code Blocks
Code blocks may use braces ( { } ) or
do/end
Ruby Talk - An Introduction to Ruby -- Linux Bangalore/2004 24

25. Code Blocks (contd.)
Example
def my_print(what)
print what
end
You cannot use braces for function
blocks
Ruby Talk - An Introduction to Ruby -- Linux Bangalore/2004 25

26. If Statement
if expression
code block
elsif (expression)
code block
else
code block
end
Ruby Talk - An Introduction to Ruby -- Linux Bangalore/2004 26

27. While Statement
while expression
code block
end
Example:
count = 1
while count < 10
print count
count += 1
end
Ruby Talk - An Introduction to Ruby -- Linux Bangalore/2004 27

28. For Loop
for variable_name in range
code block
end
Example:
for count in 0..2
print count
end
Ruby Talk - An Introduction to Ruby -- Linux Bangalore/2004 28

29. Iterators
array_or_range = value
array_or_range.each { |x|
print x
}
Example:
my_range = 1..5
my_range.each { |x|
print x
}
Ruby Talk - An Introduction to Ruby -- Linux Bangalore/2004 29

30. Functions
Functions begin with the keyword def
def function_name([args])
code block
end
Example:
def print_name(name='Ruby')
print name
end
Ruby Talk - An Introduction to Ruby -- Linux Bangalore/2004 30

31. OO Ruby
Classes are containers for static data
members and functions
Declared using the class keyword. All class
names should begin with a capital letter
Constructor declared using the initialize
keyword
Class variables precede with an “@”
Objects created using the new method
Ruby Talk - An Introduction to Ruby -- Linux Bangalore/2004 31

32. Example class
class My_class
def initialize(arg1, arg2)
@arg1 = arg1
@arg2 = arg1
end
def print_arg1()
print @arg1
end
def print_foo()
print quot;I Love Ruby!quot;
end
private
def print_arg2()
print @arg2
end
end
my_object = My_class.new(2, 3)
my_object.print_arg1
my_object.print_arg2 # will cause an exception
Ruby Talk - An Introduction to Ruby -- Linux Bangalore/2004 32

33. Inheritance
class Derived_class < My_class
def initialize()
@arg = quot;I Love Ruby!quot;
end
def print_arg()
print @arg
end
end
my_object = Derived_class.new
my_object.print_foo
Ruby Talk - An Introduction to Ruby -- Linux Bangalore/2004 33

34. Notes on OO Ruby
Access specifiers: public,
protected, private
Multiple inheritance not possible
Ruby Talk - An Introduction to Ruby -- Linux Bangalore/2004 34

35. Ruby modules
require 'net/http'
superclass
subclass
Ruby Talk - An Introduction to Ruby -- Linux Bangalore/2004 35

36. Advanced topics
Regular expressions
Network programming
MT programming
GUI programming (using Tk)
Web programming
Ruby Talk - An Introduction to Ruby -- Linux Bangalore/2004 36

37. Now what?
What you can do now?
Get your hands dirty with Ruby
Write simple Ruby programs
What you have to do?
Explore Ruby modules
Find a problem, and Ruby it!
Ruby Talk - An Introduction to Ruby -- Linux Bangalore/2004 37

38. Perl compared to Ruby
Complicated OO
Cryptic code
(Ruby is often called “A Better Perl”)
PS: Don’t kill me!
Ruby Talk - An Introduction to Ruby -- Linux Bangalore/2004 38

39. Python compared to Ruby
Incomplete OO
Instance variables require self.var
No class method
No true GC (uses ref counting)
Not suitable for one-liners
PS: Don’t kill me!
Ruby Talk - An Introduction to Ruby -- Linux Bangalore/2004 39

40. Resources
Ruby Home Page
http://www.ruby-lang.org/en/
Programming Ruby
http://www.rubycentral.com/book/
RubyGarden
http://www.rubygarden.org/ruby
Ruby Application Archive (RAA)
http://raa.ruby-lang.org/
Ruby Talk - An Introduction to Ruby -- Linux Bangalore/2004 40

41. Resources (contd.)
RubyForge
http://rubyforge.org/
ruby-talk
http://blade.nagaokaut.ac.jp/ruby/ruby-talk
Ruby Talk - An Introduction to Ruby -- Linux Bangalore/2004 41

42. If God did OOP, he’d probably do it in
Python; He’s now considering switching
to Ruby!
Ruby Talk - An Introduction to Ruby -- Linux Bangalore/2004 42

43. Thank you!
Questions?
Ruby Talk - An Introduction to Ruby -- Linux Bangalore/2004 43