Programming language Ruby and the Rails framework

Ruby
programming language
and
Ruby on Rails framework

Presentation Agenda
 What is Ruby?

 About the language

 Its history

 Principles of language

 Code examples

 Rails framework

January 18, 2010 Radek Mika - Unicorn College 2

What is Ruby?
 Programming language

 Interpreted language

 Modern language

 Object-oriented language

 Dynamically typed language

 Agile language


Principles of Ruby


Principles of Ruby
 Japanese Design

 Focus on human factor

 Principle of Least Surprise

 Principle of Least Effort


The Principle of Least Surprise
This principle is the supreme design goal of Ruby
 It makes programmers happy
 It makes Ruby easy to learn
Examples
 What class is an object?
o.class
 Is it Array.size or Array.length?
same method - they are aliased
 What are the differences between arrays?
Diff = ary1 – ary2
Union = ary1 + ary2


The Principle of Least Effort
 We do not like to waste time
Especially on XML configuration files, getters, setters, etc.

 Syntactic sugar wherever you look

 The quicker we program, the more we accomplish
Sounds reasonable enough, does not it?

 Less code means less bugs


Philosophy
 No perfect language

 Have joy

 Computers are my servants, not my masters!

 Unchangeable small core (syntax) and extensible class
libraries


The History of Ruby
 Created in Japan 10 years ago

 Created by Yukihiro Matsumoto (known as
Matz)

 Inspired by Perl, Python, Lisp and Smalltalk


Comparison with Python
 Interactive prompt (similar)
 No special line terminator (similar)
 Everything is an object (similar)

X
 More speed! (ruby is faster)
…

Ruby is Truly Object-Oriented
 Ruby uses single inheritance
X
 Mixins and Modules allow you to extend classes
without multiple inheritance

 Reflection

 Things like ‘=’ and ‘+’ which may appear as
operators are actually methods (like Smalltalk)


Well, that’s all nice but…

…is it FAST?

Merge Sort Algorithm


Ruby Speed Comparison

3x faster than PHP

2.5x faster than Perl

2x faster than Python

2x (maybe more) C++
SLOWER than


Ruby Speed - WARNING

Previous results are only
informational (only Merge Sort
Comparison)

Another comparisons usually
have different results


When I should not use Ruby?
 If I need highly effective and powerful language, e.g.
for distributed calculations
 If I want to write a complicated, ugly or messy code

Other disadvantages:

 Less spread than Perl is
 Ruby is relatively slow


And finally…

…some code examples

Clear Syntax
# Output "UPPER"
puts "upper".upcase

# Output the absolute value of -5:
puts -5.abs

# Output "Ruby Rocks!" 5 times
5.times do
puts "Ruby Rocks!"
end
Source: http://pastie.org/785234


Classes and Methods
#Classes begin with class and end with end:
# The Greeter class
class Greeter
end

#Methods begin with def and end with end:
# The salute method
def salute
end
Source: http://pastie.org/785249


Classes and Methods
# The Greeter class
class Greeter
def initialize(greeting)
@greeting = greeting
end

def salute(name)
puts "#{@greeting} #{name}!"
end
end

# Initialize our Greeter
g = Greeter.new("Hello")

# Output "Hello World!"
g.salute("World")

Source: http://pastie.org/785258 - classes


If Statements
# if with several branches
if account.total > 100000
puts "large account"
elsif account.total > 25000
puts "medium account"
else
puts "small account„
end
Sources: http://pastie.org/785268


Case Statements
# A simple case/when statement
case name
when "John"
puts "Howdy John!"
when "Ryan"
puts "Whatz up Ryan!"
else
puts "Hi #{name}!"
end


Regular Expressions
#Ruby supports Perl-style regular expressions:
# Extract the parts of a phone number

phone = "123-456-7890"

if phone =~ /(d{3})-(d{3})-(d{4})/
ext = $1
city = $2
num = $3
end


Regular Expressions
# Case statement with regular expression
case lang
when /ruby/i
puts "Matz created Ruby!"
when /perl/i
puts "Larry created Perl!"
else
puts "I don't know who created #{lang}."
end


Ruby Blocks
# Print out a list of people from
# each person in the Array
people.each do |person|
puts "* #{person.name}"
end

# A block using the bracket syntax
5.times { puts "Ruby rocks!" }

# Custom sorting
[2,1,3].sort! { |a, b| b <=> a }

Sources: http://pastie.org/pastes/785239


Yield to the Block!
# define the thrice method
def thrice
yield
yield
yield
end

# Output "Blocks are cool!" three times
thrice { puts "Blocks are cool!" }

#This example use yield from within a method to
#hand control over to a block:


Blocks with Parameters
# redefine the thrice method
def thrice
yield(1)
yield(2)
yield(3)
end

# Output "Blocks are cool!" three times,
# prefix it with the count
thrice { | i |
puts "#{i}: Blocks are cool!"
}


Enough talking about Ruby!...

What about Ruby on Rails?

Ruby on Rails
 Web framework

 An extremely productive web-application
framework that is written in Ruby by
David Hansson

 Includes everything needed to create database-driven web
applications according to the Model-View-Control pattern
of separation

 So-called reason of spreading ruby


Ruby on Rails
 MVC

 Convention over Configurations

 Don’t Repeat Yourself (DRY)


History
 Predominantly written by David H. Hannson
 Talented designer
 His dream is to change the world
 A 37signals.com principal – World class designers

 Since 2005


Model – View - Controller
 MVC is an architectural pattern, used not only for building web
applications

 Model classes are the "smart" domain objects (such as Account,
Product, Person, Post) that hold business logic and know how to
persist themselves to a database

 Views are HTML templates

 Controllers handle incoming requests (such as Save New Account,
Update Product, Show Post) by manipulating the model and
directing data to the view


Active Record
Object/Relational Mapping Framework = Active Record

 Automatic mapping between columns and class
attributes
 Declarative configuration via macros
 Dynamic finders
 Associations, Aggregations, Tree and List Behaviors
 Locking
 Lifecycle Callbacks
 Single-table inheritance supported
 Validation rules


From Controller to View
Rails gives you many rendering options

 Default template rendering
Just follow naming conventions and magic happens.

 Explicitly render to particular action

 Redirect to another action

 Render a string response (or no response)

View Template
ERB –Embedded Ruby

 Similar to JSPs <% and <%= syntax

 Easy to learn and teach for designers

 Execute in scope of controller

 Denoted with .rhtml extension


View Template
XmlMarkup –Programmatic View Construction

 Great for writing xhtml and xml content

 Denoted with .rxml extension

 Embeddable in ERB templates


And Much More…
 Templates and partials
 Pagination
 Caching (page, fragment, action)
 Helpers
 Routing with routes.rb
 Exceptions
 Unit testing
 ActiveSupport API (date conversion, time calculations)
 ActionMailer API
 ActionWebService API
 Rake


Sources
 Ruby on Rails (Agile Atlanta Group) – Obie Fernandez – May 10 ’05
 Ruby Language Overview – Muhamad Admin Rastgee
 Ruby on Rails – Curt Hibbs
 Workin’ on the Rails Road – Obie Fernandez
 Get to the Point! (Development with Ruby on Rails) – Ryan Platte, John W. Long

 Ruby speed comparison (http://is.gd/70hjD)

 http://en.wikipedia.org/wiki/Ruby_on_Rails


External Links
 http://ruby-lang.org – official website

 http://www.ruby-doc.org/ - Ruby doc project

 http://rubyforge.org/ - projects in Ruby

 http://www.rubycentral.com/book/ - online book Programming Ruby

 Full Ruby on Rails Tutorial

 Euruko 2008 - videos from European Ruby Conference 2008 in Prague on avc-
cvut.cz (Czech)


Between Q&A…
… you can run this code …

… do you still think that you have a fast computer? :)


Acknowledgments & Contact

Special thanks to Mgr. Veronika Kaplanová for English correction.

Radek Mika
radek@radekmika.cz
@radekmika (twitter)


Programming language Ruby and the Rails framework

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