RUBY - 101Lets learn Ruby

Hi, I’m Harisankar P S

Known in the world wide web as @coderhs

Cochin, India

I program in Ruby and Rails for living :)

I am also the founder and CEO of

An exclusive Ruby based software development company

Kerala Ruby User Group@keralarbhttp://krug.github.io

A group of people who loves working, learning and talking about Ruby.

We have been active for the last three years.

We meet every 3rd sunday

So thank you guys for hosting the meetup for April, 2015.

With a bit of Historyso lets begin

– Matz, the creator of Ruby

"Ruby makes programmers happy"

Yukihiro Matsumoto aka Matz

He created ruby in 1993 Released to the public is 1995. First public version was 0.95

It was developed in Japan.

First english mailing list was created in 1999

Ruby is build to be as natural as possible.

So that we can avoid the above conversation

puts “Hello World”

Step 1 : Hello World

Numbers2 + 2 #=> 4

2 + 3.15 #=> 5.14

2 ** 100 #=> 1267650600228229401496703205376

# The largest number ruby can handle it the largest # number your system can store

What about data types?

• Everything in Ruby is an Object

• 2.class #=> Fixnum

• 3.14.class #=> Float

• (2**100).class #=> Bignum

Variables

x = 1 # x is an integer (class FixNum)

x = x + 1.5 # x is now a Float

x = 'Ruby' # Now a string

puts "Hello, #{x}!" #=> 'Hello, Ruby!'

Strings

'Hello, world!'

'Hello'.class #=> String

'Hello'.size #=> 5

Arrays

items = [1, 2, 3]

items << 'a' #=> [1, 2, 3, ‘a']

x = items.pop #=> 'a'

items #=> [1, 2, 3]

items.push 4 #=> [1, 2, 3, 4]

Ranges

(1..3)

(1..3).class #=> Range

(1..3).to_a #=> [1, 2, 3]

Hashesperson = {

name: 'Matz',

languages: ['C', 'Python', 'Ruby']

}

# OR

person = { 'Matz' }

person[:languages] = ['C', 'Python', 'Ruby']

Iteration

(0..2).each do |i| puts i*2 end

Conditions

if x == 2

do_something()

end

do_something if x == 2

Conditions

do_something if x == true

do_something if x

Functions

def sqare(x)

x*x

end

square(3) #=> 9

Enumerables

list = (1..3)

squares = list.map { |i| i * 2 } #=> [1, 4, 9]

Enumerables

list = (1..3)

squares = list.map :square #=> [1, 4, 9]

Enumerables

list = (1..3)

squares = list.reduce :+

Enumerables

(1..5).select { |i| i%2 == 0 } #=> [2, 4]

(1..5).reject { |i| i%2 == 0 } #=> [1, 3, 5]

Enumerables

(1..5).select :even? #=> [2, 4]

(1..5).reject :even? #=> [1, 3, 5]

Blocksdef foo

puts 'Before yield'

yield

puts 'After yield'

end

foo { puts 'Inside the block' }

#=> Before yield

#=> Inside the block

#=> After yield

Procs

foo = Proc.new do

puts 'Hello'

end

proc.call

Lambda

hello = lambda { |x| puts "Hello, #{x}!" }

hello.call 'world' #=> Hello, world!

Objects and classes

Objects and classesclass Dog

def greet

'Woof!'

end

end

dog = Dog.new

dog.greet #=> 'Woof!'

Instance variablesclass Dog

def name=(n)

@name = n

end

def greet

"Woof, I'm #{@name}"

end

end

dog = Dog.new

dog.name = 'Scooby'

Constructorsclass Dog

def initialize(name)

@name = name

end

def greet

"Woof, I'm #{@name}"

end

end

dog = Dog.new 'Scooby'

dog.greet #=> 'Woof! I'm Scooby.'

Class variablesclass Cat

@@sound = 'Meow'

def greet

@sound

end

end

garfield = Cat.new

garfield.greet #=> 'Meow!'

Attribute accessorsclass Dog

def name=(name)

@name = name

end

def name

@name

end

end

Attribute accessorsclass Dog

attr_accessor :name

end

# Also

# * attr_reader

# * attr_writer

Open classesclass Fixnum

def plus_five

self + 5

end

end

1.plus_five #=> 6

Inheritanceclass Animal

def initialize(name)

@name = name

end

def greet

'Hello!'

end

end

Inheritanceclass Dog < Animal

def greet

"Hello, I'm #{@name}! Woof, woof!"

end

end

goofy = Dog.new('Goofy')

goofy.greet #=> "Hello, I'm Goofy! Woof, woof!"

Inheritanceclass Cat < Animal

# do nothing here

end

tom = Dog.new('Tom')

tom.greet #=> "Hello!"

Class methodsclass Dog

def self.default_greeting

'Woof!'

end

end

Dog.default_greeting #=> 'Woof!'

Singletonsclass Dog

def greet

'Woof'

end

end

scooby = Dog.new

scooby.greet #=> 'Woof'

Singletons

# ... contd

def scooby.greet

'Scooby Doo!'

end

scooby.greet #=> 'Scooby Doo!'

Modules - extendmodule Speech

def greeting

'Hello'

end

end

class Dog

extend Speech

end

Dog.greeting #=> 'Hello'

Modules - includemodule Speech

def greet

'Hello'

end

end

class Dog

include Speech

end

dog = Dog.new

dog.greet #=> 'Hello'

method_missingclass Dog

def method_missing(method_name, *args)

"Ï don't understand!"

end

end

scooby = Dog.new

scooby.hello #=> "I don't understand!"

method_missingclass Dog

def method_missing(method_name, *args)

if method_name.to_s =~ /^say_(.*)/

"Dog says: #{$1}"

end

end

end

scooby = Dog.new

scooby.hello #=> nil

scooby.say_hello #=> 'Dog says: hello'

Want to Learn More?

Websites

• rubymonk.com

• rubylearning.com

• tryruby.org

Books

• Why's Poignant Guide to Ruby

• Humble Little Ruby Book

creditsThis presentation is built using information from

• Ruby 101 - Nithin Bekal (http://nithinbekal.com/slides/ruby-101)

• Lets Learn Ruby (http://www.slideshare.net/aquarianboy/lets-learn-ruby-basic)

• Ruby Basics (http://www.slideshare.net/Robertdennyson/ruby-basics)