launchkit-codes

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

launchkit-codes

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

class Node
  attr_accessor :left, :right, :value

launchkit-codes

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

def return_hello
  return Hello
end

launchkit-codes

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

# output
#
# 'lol'

launchkit-codes

# require_relative :
#
# Ruby tries to load the library named string relative to the requiring file’s path.
# If the file’s path cannot be determined a LoadError is raised.
# If a file is loaded true is returned and false otherwise.
#
# Tree directory:
#
# ./
# |- test

launchkit-codes

# `puts` method calls `to_s` method when a class is given as param
# `p` method calls `inspect` method when a class is given as param

class Factory
  def initialize
    @workers  = { workers: [] }   # A lot of workers
    @machines = { machines: [] }  # A lot of machines
  end

  def add_worker(name)

launchkit-codes

# Gemfile consists of plain Ruby
# So it's authorized to do this:

branch = 'develop'

group :development do
  %(a b c d).each do |lib|
    gem lib, :git => "https://github.com/abc/#{lib}.git", :branch => branch
  end
end

launchkit-codes

# more information here: http://ruby-doc.org//core-2.2.0/Integer.html#method-i-chr

puts 219.chr                  #=> "?"
puts 219.chr(Encoding::UTF_8) #=> "Û"

launchkit-codes

class ValentineDay
  def to_s
    "I love you"
  end
end

puts "#{ValentineDay.new}" # => I love you

launchkit-codes

def add(a)
  return Proc.new do |b|
    a + b
  end
end

addition = add(4)

puts addition.call(5) # => 9