Introduction to Ruby

Ruby Programming

What is Ruby ? • Ruby – Object Oriented Programming Language • Written 1995 by Yukihiro Matsumoto • Influenced by Python,Pearl,LISP • Easy to understand and workwith • Simple and nice syntax • Powerful programming capabilities #

Advantages • Powerful And Expressive • Rich Library Support • Rapid Development • Open Source • Flexible and Dynamic

Install Ruby • On Fedora – Rpms are available • ruby-1.8.6.287-8.fc11.i586 • ruby-devel • ruby-postgres • ruby-docs • ruby-racc • ruby-docs #

Types • Command “ruby” • The extension is .rb #

Ruby Documents • Command ri • Example – ri class – #

helloPerson.rb • # First ruby programme • def helloPerson(name) • result = "Hello, " + name • return result • end • puts helloPerson("Justin") #

Execute Programme • $ ruby helloPerson.rb • Hello, Justin • Nice and simple • Can use irb – interactive ruby shell • # is for comments like // #

Ruby variables • def returnFoo • bar = "Ramone, bring me my cup." • return bar • end • puts returnFoo • #

Kinds of Variables • Global variable - $ sign • instance variable - @ sign • Class Variable - @@ sign • Local Variable – no sign • Constants – Capital Letters #

Global Variable • Available everywhere inside a programme • Not use frequently #

instance variable • Unique inside an instance of a class • Truncated with instance • @apple = Apple.new • @apple.seeds = 15 • @apple.color = "Green" • #

• class Course Classes • def initialize(dept, number, name, professor) • @dept = dept • @number = number • @name = name • @professor = professor • end • def to_s • "Course Information: #@dept #@number - #@name [#@professor]" • end • def • self.find_all_students • ... • end • end #

Classes • Initialize – is the constructor • Def – end -> function • Class-end -> class #

Define Object • class Student • def login_student • puts "login_student is running" • end • private • def delete_students • puts "delete_students is running" • end • protected • def encrypt_student_password • puts "encrypt_student_password is running" • end • end #

Define Object • @student = Student.new • @student.delete_students # This will fail • Because it is private • #

Classes consist of methods and instance variables • class Coordinate • def initialize(x,y) #constructor • @x = x # set instance variables • @y = y • end • def to_s # string representation • "(#{@x},#{@y})" • end • end • point = Coordinate.new(1,5) • puts point • Will output (1,5) #

Inheritance • class AnnotatedCoordinate < Coordinate • def initialize(x,y,comment) • super(x,y) • @comment = comment • end • def to_s • super + "[#@comment]" • end • End • a_point = • AnnotatedCoordinate.new(8,14,"Centre"); • puts a_point • Out Put Is -> (8,14)[Centre] #

Inheritance • Inherit a parent class • Extend functions and variables • Add more features to base class #

Polymorphism • The behavior of an object that varies depending on the input. • • #

Polymorphism • class Person • # Generic features • end • class Teacher < Person • # A Teacher can enroll in a course for a semester as either • # a professor or a teaching assistant • def enroll(course, semester, role) • ... • end • end • class Student < Person • # A Student can enroll in a course for a semester • def enroll(course, semester) • ... • end • end #

Calling objects • @course1 = Course.new("CPT","380","Beginning Ruby Programming","Lutes") • @course2 = GradCourse.new("CPT","499d","Small Scale Digital Imaging","Mislan", "Spring") • p @course1.to_s • p @course2.to_s #

Calling Objects • @course1 that contains information about a Course • @course2 is another instance variable, but it contains information about a GradClass object • #

Arrays and hashes • fruit = ['Apple', 'Orange', 'Squash'] • puts fruit[0] • fruit << 'Corn' • puts fruit[3] #

Arrays • << will input a new element • Last line outputs the new element #

Arrays More... • fruit = { • :apple => 'fruit', • :orange => 'fruit', • :squash => 'vegetable' • } • puts fruit[:apple] • fruit[:corn] = 'vegetable' • puts fruit[:corn] #

Arrays More... • h = {"Red" => 1, "Blue" => 2, "Green" => 3} • CORPORATE • p h["Red"] • Outpus -> 1 • h["Yellow"] = 4 • p h["Yellow"] • Outputs -> 4 #

Decision structures • age = 40 • if age < 12 • puts "You are too young to play" • elsif age < 30 • puts "You can play for the normal price" • elsif age == 35 • puts "You can play for free" • elsif age < 65 • puts "You get a senior discount" • else • puts "You are too old to play" • end #

while • clock = 0 • while clock < 90 • puts "I kicked the ball to my team mate in the " + count.to_s + " • minute of the match." • clock += 1 • end #

Iterators • fruit = ['Apple', 'Orange', 'Squash'] • fruit.each do |f| • puts f • end #

Iterators • Keyword - do - • Instance variable |f| • Print f means print the instance of the loop #

Iterators • fruit = ['Apple', 'Orange', 'Squash'] • fruit.each_with_index do |f,i| • puts "#{i} is for #{f}" • end • #

Iterators • Here f is the instance • Index is i • Will get two variables #

Iterators • fruit = ['Apple', 'Orange', 'Squash'] • for i in 0...fruit.length • puts fruit[i] • end • #

Iterators • For loop • Same old syntax • But 'each' loop is smart to handle an array • 'each' dont need a max cutoff value. #

case...when • temperature = -88 • case temperature • when -20...0 • puts "cold“; start_heater • when 0...20 • puts “moderate" • when 11...30 • puts “hot”; drink_beer • else • puts "are you serious?" • end #

Exception handling • begin • @user = User.find(1) • @user.name • rescue • STDERR.puts "A bad error occurred" • end • #

Thanks #

http://smashingweb.ge6.org	26
http://ranjith.zfs.in	20
http://www.slideshare.net	11
http://smashingweb.info	5

Introduction to Ruby

by Ranjith siji on Dec 29, 2009

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