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# Ruby Method-Calling Hierarchy.
#
# When a method is called Ruby :
#
# 1 - searches the method in class.
#
# 2- searches the method in each included modules
#    from the last one to the first one.
#
# Study Case:

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# 
# Main difference: Procs are objects, blocks are not.
#
# The '&' tells ruby to turn the proc into a block.
#

class Array
  def map2
    new_ary = []
    self.each do |elem|

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require "net/http"

uri = URI('YOUR URL')

req = Net::HTTP::Head.new(uri)

res = Net::HTTP.start(uri.hostname, uri.port) do |http|
  http.request(req)
end

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<%= link_to "Name", sort: "Name" %>
<%= link_to "Price", sort: "price" %>
<%= link_to "Popular", sort: "popular" %>

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# Example:
#
# Wanna pass an array of categories via a GET request.

http://YOUR_URL/?category[]=handbag&category[]=wallet

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# Procs and Lambdas. They are both a Proc object.
#
# The main differences:
#
# 1- Lamdbas are strict about argument number instead of Procs.
# 2- Lambda :return returns out the scope. Proc :return returns out of the calling scope.

# Lamdbas are strict about argument number instead of Procs.
l = lambda { |word| puts word }

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class Category < ActiveRecord::Base
  has_and_belongs_to_many :products
end

class Product < ActiveRecord::Base
  has_and_belongs_to_many :categories
  
  # :c can be an array of categories.
  scope :by_categories, ->(c) { includes(:categories).where(categories: {id: c})  }
end

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# Example:
#
#     1
#    / \
#   2  12
#  /
# 4

class Node
  attr_accessor :left, :right, :value

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class Hello
  def self.world
    puts 'Hello World !'
  end
end

def return_hello
  return Hello
end

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"olo".gsub(/[ol]/, 'o' => 'l', 'l' => 'o')

# output
#
# 'lol'