intro to ruby

Ruby

The Ruby Language

• Originally by Yukihiro "Matz" Matsumoto• “Ruby is designed for programmer

productivity and fun, following the principles of good user interface design. He stresses that systems design needs to emphasize human, rather than computer, needs.”

http://en.wikipedia.org/wiki/Ruby_(programming_language)#History

• Ruby 1.0 was released in 1996.

Ruby Language Overview

• Dynamically typed• Interpreted• Can be modified at runtime• Object oriented• Blocks & lambdas• Nice support for Regular Expressions

Lets get started

• IRB: InteractiveRuBy>> 4>> 4 + 4

Everything is an object

“test”.upcase“test”.class“test”.methods

Everything evaluates to something

2 + 2(2+2).zero?

Methods are Messages

thing.do(4)thing.do 4thing.send “do”, 4

Operators are Methods

thing.do 4thing.do(4)thing.send “do”, 4

1 + 21.+(2)1.send "+", 2

Write your first Ruby class

Conditionals, Iterators & Blocks

With Hashes & Arrays

CONDITIONALS

Conditionals: ifif age > 17puts “can vote”

end

if age > 17puts “can vote”

elseputs “attends school”

end

Statement Modifiers:y = 7 if x == 4

Other Syntax:if x == 4 then y = 7

end

Truth• Truth: Everything is true except for:– false – nil

• Therefore– 0 is true– “” is true

• Checking for false:if !(name == “superman”) …if not (name == “superman”) …

Unless

• “unless” provides us with another way of checking if a condition is false:

unless superpower == nilstatus = “superhero”

end

Case

case superherowhen “superman”

city = “metropolis”when “batman”

city = “gotham_city”else

city = “central_city”end

Case Refactoring

city = case superherowhen “superman”

“metropolis”when “batman”

“gotham_city”else

“central_city”end

ITERATORS

Iterators: Conditional Looping

• “while” allows us to loop through code while a set condition is true

x = 1while x < 10puts x.to_s + “ iteration”x += 1

end

Creating a new array

x = [1, 2, 3, 4]=> [1, 2, 3, 4]

x = %w(1 2 3 4) => [“1”, “2”, “3”, “4”]

chef = Array.new(3, “bork”)=> [“bork”, “bork”, bork”]

Accessing Array Values

a = [ "a", "b", "c", "d", "e" ] a[0] #=> "a”

a[2] #=> "c”

a[6] #=> nil

Creating a Hash

h = { "a" => 100, "b" => 200 }h[“a”]

h = { 1 => “a”, “b” => “hello” }h[1]

Operations on Hashes: Merge

h1 = { "a" => 100, "b" => 200 } => {"a"=>100, "b"=>200}h2 = { "b" => 254, "c" => 300 }=>{"b"=>254, "c"=>300}

h3 = h1.merge(h2)=> {"a"=>100, "b"=>254, "c"=>300}h1=> {"a"=>100, "b"=>200}

h1.merge!(h2)=> {"a"=>100, "b"=>254, "c"=>300}

Operations on Hashes

h = { "a" => 100, "b" => 200 } h.delete("a”)

h = { "a" => 100, "b" => 200, "c" => 300, "d" => 400 }

letters = h.keys

h = { "a" => 100, "b" => 200, "c" => 300 }

numbers = h.values

Times

5.times{ puts “hello” }

99.times do |beer_num| puts "#{beer_num} bottles

of beer”end

Eachsuperheroes = [“catwoman”, “batman”, “wonderwoman”]superheroes.each do | s |

puts “#{ s } save me!” end

wonderwoman save me!batman save me!catwoman save me!

BLOCKS

Blocks

def dos_veces yield yieldend

dos_veces { puts "Hola” }

HolaHola

This is a Block!

{Yield executes the block

Yield with Parameters

def bandsyield(“abba”, “who”)

end

bands do |x,y| puts x,y

end

abbawho

Yield sends its parameters as arguments to the block

yield(“abba”, ”who”) sends “abba” and “who” to |x, y|

x is set to “abba”

y is set to “who”

Ruby Koansa walk along the path to enlightenment

http://github.com/edgecase/ruby_koans

Mr. Neighborly's Humble Little

Ruby BookJeremy McAnally

The Well-Grounded RubyistCovering Ruby 1.9

David A. Black