Ruby Talk

1
Ruby Talk An Introduction to

• Premshree Pillai
• premshree_at_livejournal.com

2
Scope of Talk

• What this talk is and what it isnt
• Me, myself
• What is?
• Why use?
• How to? (a quick run through the syntax)
• Quick comparisons (with Perl and Python)
• Resources

3
Purpose

• What this talk is?
• Get you interested
• Get you started with Ruby
• What it isnt?
• Not a tutorial

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

5
History (Rubys, 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

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

7
Where can you use Ruby?

• System (n/w, RegExps)
• Web programming (using CGI)
• Agents, crawlers
• DB programming (using DBI)
• GUI (Tk, RubyMagick)

8
General Features

• High level language
• True OO (everythings an object!)
• Interpreted
• Portable
• Low learning curve
• A quick scan thro the syntax

9
Running Ruby

• From the command line
• ruby file.rb
• Windows binary comes bundled with Scintilla

10
Basic stuff

• print 'Hello, world!'
• p 'Hello, world!' prints with newline
• my_var gets get input

11
Operators

• (addition)
• - (subtraction/negation)
• (multiplication)
• / (division)
• (modulus)
• (exponentiation)

12
Operators (contd.)

• ltgt (returns -1, 0 or 1)
• lt, lt, gt, gt
• (matching)
• eql? (test of equality of type and values)

13
Operators (contd.)

• and -- are not reserved operators
• Use and -

14
Logical Operators

• and
• or
• not

15
Typing

• Dynamic typed
• Type checking at run-time
• Strong typed

16
Basic Data Types

• Integers and floats
• Strings
• Ranges
• Arrays
• Hashes

17
Strings

• my_str 'whatever'
• my_str "blah, blah"
• my_str.split(",")0.split("")2 3

18
Ranges

• Inclusive range
• my_range 1 .. 3
• my_range 'abc' .. 'abf'
• Non-inclusive range
• my_range 1 5
• my_range 'abc' 'abf'

19
Arrays

• my_array 1, 2, 3
• Common methods
• my_array.length
• my_array ltlt 4
• my_array0, etc.

20
Hashes

• my_hash
• 'desc' gt 'color' gt 'blue',,
• 1 gt 1, 2, 3
• print my_hash'desc''color'
• will return
• blue

21
Hashes (contd.)

• Common methods
• my_hash.keys
• my_hash.values

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

23
Everything's an Object

• Methods can be applied to data directly not
  just on variables holding data
• Example
• 5.to_s will return "5"

24
Code Blocks

• Code blocks may use braces ( ) or do/end

25
Code Blocks (contd.)

• Example
• def my_print(what)
• print what
• end
• You cannot use braces for function blocks

26
If Statement

• if expression
• code block
• elsif (expression)
• code block
• else
• code block
• end

27
While Statement

• while expression
• code block
• end
• Example
• count 1
• while count lt 10
• print count
• count 1
• end

28
For Loop

• for variable_name in range
• code block
• end
• Example
• for count in 0..2
• print count
• end

29
Iterators

• array_or_range value
• array_or_range.each x
• print x
• Example
• my_range 1..5
• my_range.each x
• print x

30
Functions

• Functions begin with the keyword def
• def function_name(args)
• code block
• end
• Example
• def print_name(name'Ruby')
• print name
• end

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 _at_
• Objects created using the new method

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Example class

• class My_class
• def initialize(arg1, arg2)
• _at_arg1 arg1
• _at_arg2 arg1
• end
• def print_arg1()
• print _at_arg1
• end
• def print_foo()
• print "I Love Ruby!"
• end
• private
• def print_arg2()
• print _at_arg2
• end
• end
• my_object My_class.new(2, 3)
• my_object.print_arg1

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Inheritance

• class Derived_class lt My_class
• def initialize()
• _at_arg "I Love Ruby!"
• end
• def print_arg()
• print _at_arg
• end
• end
• my_object Derived_class.new
• my_object.print_foo

34
Notes on OO Ruby

• Access specifiers public, protected, private
• Multiple inheritance not possible

35
Ruby modules

• require 'net/http'

superclass
subclass
36
Advanced topics

• Regular expressions
• Network programming
• MT programming
• GUI programming (using Tk)
• Web programming

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!

38
Perl compared to Ruby

• Complicated OO
• Cryptic code
• (Ruby is often called A Better Perl)
• PS Dont kill me!

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 Dont kill me!

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/

41
Resources (contd.)

• RubyForge
• http//rubyforge.org/
• ruby-talk
• http//blade.nagaokaut.ac.jp/ruby/ruby-talk/index
  .shtml

42

• If God did OOP, hed probably do it in Python
  Hes now considering switching to Ruby!

43

• Thank you!
• Questions?