Ruby and Rails by example

Ruby is simple in appearance,
but is very complex inside,
just like our human body.
- Yukihiro "matz" Matsumoto,
creator of Ruby

// Using C#

using System;
using System.Collections;

...

Hashtable openWith = new Hashtable();

openWith.Add("txt", "notepad.exe");
openWith.Add("bmp", "paint.exe");
openWith.Add("dib", "paint.exe");
openWith.Add("rtf", "wordpad.exe");

# Using Ruby

openWith = { "txt" => "notepad.exe",
"bmp" => "paint.exe",
"dib" => "paint.exe",
"rtf" => "wordpad.exe" }

# Using Ruby 1.9

openWith = { txt: "notepad.exe",
bmp: "paint.exe", dib: "paint.exe",
rtf: "wordpad.exe" }

Example 2:
Create a Binary Tree

class Node
attr_accessor :value

def initialize(value = nil)
@value = value
end

attr_reader :left, :right
def left=(node); @left = create_node(node); end
def right=(node); @right = create_node(node); end

private
def create_node(node)
node.instance_of? Node ? node : Node.new(node)
end
end

Example 2.1:
Traverse the
Binary Tree

def traverse(node)
visited_list = []
inorder(node, visited)
puts visited.join(",")
end

def inorder(node, visited)
inorder(node.left, visited) unless node.left.nil?
visited << node.value
inorder(node.right, visited) unless node.right.nil?
end

def traverse(node)
visited_list = []
inorder node, visited
puts visited.join ","
end

def inorder(node, visited)
inorder node.left, visited unless node.left.nil?
visited << node.value
inorder node.right, visited unless node.right.nil?
end

Example 3:
Create a Person →
Student →
College Student
class hierarchy

class Person
attr_accessor :name
end

class Student < Person
attr_accessor :school
end

class CollegeStudent < Student
attr_accessor :course
end

x = CollegeStudent.new
x.name = "John Doe"
x.school = "ABC University"
x.course = "Computer Science"

Example 4:
Call a method in a
"primitive"

nil.methods

true.object_id

1.upto(10) do |x|
puts x
end

Example 5:
Find the sum of the
squares of all numbers
under 10,000 divisible
by 3 and/or 5

x = 1
sum = 0
while x < 10000 do
if x % 3 == 0 or x % 5 == 0
sum += x * x
end
end
puts sum

puts (1..10000).
select { |x| x % 3 == 0 or x % 5 == 0}.
map {|x| x * x }.
reduce(:+)

Example 6:
Find all employees
older than 30 and sort
by last name

oldies = employees.select { |e| e.age > 30 }.
sort { |e1, e2| e1.last_name <=> e2.last_name }

Example 7:
Assign a method to a
variable

hello = Proc.new { |string| puts "Hello #{string}" }

hello.call "Alice"

Example 8:
Add a "plus" method to
all numbers

class Numeric
def plus(value)
self.+(value)
end
end

Example 9:
Define different
behavior for different
instances

alice = Person.new
bob = Person.new

alice.instance_eval do
def hello
puts "Hello"
end
end

def bob.hello
puts "Howdy!"
end

Example 10:
Make Duck and
Person swim

module Swimmer
def swim
puts "This #{self.class} is swimming"
end
end

class Duck
include Swimmer
end

class Person
include Swimmer
end

Duck.new.swim
Student.new.swim

Example 0:
Make a Twitter Clone

$ rails new twitclone
$ cd twitclone
$ rails generate scaffold tweet message:string
$ rake db:migrate
$ rails server

Dynamic
Object Oriented
Functional
Metaprogramming

Software
Engineering
"Best Practices"

Rails Example:
Demo a Twitter Clone

https://github.com/bryanbibat/microblog31

Authentication – Devise
Attachments – Paperclip
Pagination – Kaminari
Template Engine – Haml
UI – Twitter Bootstrap

Bonus Example:
Scale the
Twitter Clone

Thank You For
Listening!
Philippine Ruby Users Group:
http://pinoyrb.org
me: http://bryanbibat.net | @bry_bibat

Ruby and Rails by example

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