Yo Dawg, Herd U Like DSLs

class_self_self.rb

class Person
  def poop
    puts "I pooped today!"
  end

  # One common way to make a class method is to declare it amongst the instance
  # methods prefixed with self...
  def self.poop!
    puts "Everybody pooped today!"
  end

  class << self
    # The other common way is to open Class:Person "with class << self" declare
    # it as an instance method in there.
    def poo!
      puts "Everybody went poo today!"
    end

    # But what happens if you declare a self. method inside << self?
    def self.poopy
      puts "Something just went poopy. I have no idea what, or where, but I suspect it was messy."
    end
  end
end

Person.new.poop
# => I pooped today!

Person.poop!
# => Everybody pooped today!

Person.poo!
# => Everybody went poo today!

# But where is "poopy"?


# No idea how to call the "poopy" method directly. If I evaluate self from
# inside the << self scope, it is #<Class:Person> but the method does not appear
# on the class interface of Person or Class. Is #<Class:Person> the
# meta/eigen/wotsitclass?

# Hmm... let's try to see where we are at each point:

# 2.2.2 :063 > class Person
# 2.2.2 :064?>   puts "Hello from #{self}"
# 2.2.2 :065?>   class << self
# 2.2.2 :066?>     puts "Hello from #{self}"
# 2.2.2 :067?>     class << self
# 2.2.2 :068?>       puts "Hello from #{self}"
# 2.2.2 :069?>       end
# 2.2.2 :070?>     end
# 2.2.2 :071?>   end
# Hello from Person
# Hello from #<Class:Person>
# Hello from #<Class:#<Class:Person>>

# AH-HA! Okay, I still don't know exactly what's going on, BUT I do know that
# instance methods declared on self inside a class become class methods on that
# class:

# 2.2.2 :077 > class Person
# 2.2.2 :078?>   poop!
# 2.2.2 :079?>   end
# Everybody pooped today!

# Okay. So again, I still don't know the WHY, but I now at least know HOW to
# call that method: as a DSL/class method from INSIDE the superclass:

# 2.2.2 :080 > class Person
# 2.2.2 :081?>   class << self
# 2.2.2 :082?>     poopy
# 2.2.2 :083?>     end
# 2.2.2 :084?>   end
# Something just went poopy. I have no idea what, or where, but I suspect it was
# messy.

# AND BOOM.

# I don't know why I would ever need this skill, and I pray that I never use it
# in anger. I'm putting this in my satchel full of rusty shivs: Sometimes I get
# cornered in a dark alley at night, and when that happens I'd rather have a
# rusty shiv than empty hands.

# TL;DR This should be called "Yo Dawg, Herd U Like DSLs, So we put a DSL in yo
# DSL so you can DSL while you DSL."