Ruby Nested Methods

nested_methods.rb

# Scott and I came across some nested classes in some code we maintain.
# We then started talking about nested methods...and then started playing.
# After a couple of "Can you?" examples we asked the important "Why would you ever do this?"
# To be clear, I think nested methods are mostly evil (I think Scott agrees)
# Still, just maybe I can create a use case where using nested methods makes sense...

# The case below is something of a social manners exercise.
# Two instances call casual greeting methods (#hi) and interact in that way.
# However, when an instance calls a formal greeting method (#hello) all instances should elevate to formal methods

# So that's what we have below. I do NOT advocate actually doing this in real code. Enjoy.

class Largeco
  class Person
    def hello
      def hi
        puts "hello"  
      end
      def bye
        puts "goodbye"
      end
      hi
    end

    def hi
      puts "hi"
    end

    def bye
      puts "bye-bye"
    end
  end
end

puts "Scott and Mark are casual"

scott = Largeco::Person.new
mark = Largeco::Person.new

puts "Scott says:"
scott.hi

puts "Mark says:"
mark.hi

puts "Scott says:"
scott.bye

puts "Mark says:"
mark.bye

puts ""
puts "BUT Chris is formal"
puts "Everyone's responses should evalevate to be Formal"
puts ""

chris = Largeco::Person.new

puts "Chris says:"
chris.hello

puts "Scott says:"
scott.hi

puts "Chris says:"
chris.bye

puts "Scott says:"
scott.bye

not_nested_methods.rb

# Below is the same exercise implemented in a type of modular fashion.
# I like it more than the previous version but still not going to advocate its use

module Formal    
  def hello
    puts "hello"
  end
  
  def hi
    hello
  end
  
  def bye
    puts "goodbye"
  end  
end

module Casual  
  def bye
    puts 'bye-bye'
  end
  
  def hi
    puts 'hi'
  end 
  
  def method_missing(method_name, *args, &block)
    if Formal.instance_methods.include?(method_name.to_s)
      self.class.send :include, Formal
      self.send method_name
    else
      super
    end
  end 
end

class Largeco
  class Person
    include Casual
  end
end

puts "Scott and Mark are casual"

scott = Largeco::Person.new
mark = Largeco::Person.new

puts "Scott says:"
scott.hi

puts "Mark says:"
mark.hi

puts "Scott says:"
scott.bye

puts "Mark says:"
mark.bye

puts ""
puts "BUT Chris is formal"
puts "Everyone's responses should evalevate to be Formal"
puts ""

chris = Largeco::Person.new

puts "Chris says:"
chris.hello

puts "Scott says:"
scott.hi

puts "Chris says:"
chris.bye

puts "Scott says:"
scott.bye

output

Scott and Mark are casual
Scott says:
hi
Mark says:
hi
Scott says:
bye-bye
Mark says:
bye-bye

BUT Chris is formal
Everyone's responses should evalevate to be Formal

Chris says:
hello
Scott says:
hello
Chris says:
goodbye
Scott says:
goodbye

How to access form nested function to variables of outer function? Is it possible in Ruby 2.4.x?