MMBJ Shanzhai Culture

R uby Talk – An Introduction to Premshree Pillai [email_address]

S cope 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

P urpose

What this talk is?

Get you interested

Get you started with Ruby

What it isn’t?

Not a tutorial

W ho am I?

(or why should you listen to me)

21/male/single :)

Technology consultant

Freelance writer since 2001

Perl/Python/Ruby/REBOL hacker

H istory (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

W hat 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

W here can you use Ruby?

System (n/w, RegExps)

Web programming (using CGI)

Agents, crawlers

DB programming (using DBI)

GUI (Tk, RubyMagick)

G eneral Features

High level language

True OO (everything’s an object!)

Interpreted

Portable

Low learning curve

A quick scan thro’ the syntax

R unning Ruby

From the command line:

ruby file.rb

Windows binary comes bundled with Scintilla

B asic stuff

print 'Hello, world!'

p 'Hello, world!' # prints with newline

my_var = gets # get input

O perators

+ (addition)

- (subtraction/negation)

* (multiplication)

/ (division)

% (modulus)

** (exponentiation)

O perators (contd.)

==

<=> (returns -1, 0 or 1)

<, <=, >=, >

=~ (matching)

eql? (test of equality of type and values)

O perators (contd.)

++ and -- are not reserved operators

Use += and +-

L ogical Operators

and

or

not

T yping

Dynamic typed

Type checking at run-time

Strong typed

B asic Data Types

Integers and floats

Strings

Ranges

Arrays

Hashes

S trings

my_str = 'whatever'

my_str = "blah, blah"

my_str.split(",")[0].split("")[2] * 3

R anges

Inclusive range

my_range = 1 .. 3

my_range = 'abc' .. 'abf'

Non-inclusive range

my_range = 1 … 5

my_range = 'abc' … 'abf'

A rrays

my_array = [1, 2, 3]

Common methods:

my_array.length

my_array << 4

my_array[0], etc.

H ashes

my_hash = {

'desc' => {'color' => 'blue',},

1 => [1, 2, 3]

}

print my_hash['desc']['color']

will return

blue

H ashes (contd.)

Common methods:

my_hash.keys

my_hash.values

D ata 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

E verything's an Object

Methods can be applied to data directly – not just on variables holding data

Example:

5.to_s will return "5"

C ode Blocks

Code blocks may use braces ( { } ) or do/end

C ode Blocks (contd.)

Example

def my_print(what)

print what

end

You cannot use braces for function blocks

I f Statement

if expression

code block

elsif ( expression )

code block

else

code block

end

W hile Statement

while expression

code block

end

Example:

count = 1

while count < 10

print count

count += 1

end

F or Loop

for variable_name in range

code block

end

Example:

for count in 0..2

print count

end

I terators

array_or_range = value

array_or_range.each { |x|

print x

}

Example:

my_range = 1..5

my_range.each { |x|

print x

}

F unctions

Functions begin with the keyword def

def function_name ( [args] )

code block

end

Example:

def print_name(name='Ruby')

print name

end

O O 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

E xample class

class My_class

def initialize(arg1, arg2)

@arg1 = arg1

@arg2 = arg1

end

def print_arg1()

print @arg1

end

def print_foo()

print " I Love Ruby! "

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

I nheritance

class Derived_class < My_class

def initialize()

@arg = "I Love Ruby!"

end

def print_arg()

print @arg

end

end

my_object = Derived_class.new

my_object.print_foo

N otes on OO Ruby

Access specifiers: public , protected , private

Multiple inheritance not possible

R uby modules

require 'net/http'

superclass subclass

A dvanced topics

Regular expressions

Network programming

MT programming

GUI programming (using Tk)

Web programming

N ow 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!

P erl compared to Ruby

Complicated OO

Cryptic code

(Ruby is often called “A Better Perl”)

PS: Don’t kill me!

P ython 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!

R esources

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/

R esources (contd.)

RubyForge

http://rubyforge.org/

ruby-talk

http://blade.nagaokaut.ac.jp/ruby/ruby-talk/index.shtml

If God did OOP, he’d probably do it in Python; He’s now considering switching to Ruby!

Thank you!

Questions?

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