gistfile1.rb

module ThemeMixin
  
=begin
  # Rails only w/ alias_method_chain
  def self.included(base)
    base.alias_method_chain(:base_method, :override)
  end
  
  def base_method_with_override
    "theme index"
  end
=end
  
  # Plain ruby - need alias_method
  def self.included(base)
    base.class_eval do
      alias_method :base_method_original, :base_method
      alias_method :base_method, :base_method_themed
    end
  end
  
  def base_method_themed
    "theme index"
  end
  
end

class App
  
  def base_method
    "index"
  end
  
  def self.remove_mixin(mod)
    mod.instance_methods.each do |method_name|
      if method_name =~ /^(.*)_themed$/
        self.class_eval do 
          alias_method $1, "#{$1}_original"
          alias_method "#{$1}_themed", $1
        end
      end
    end
  end
  
end

puts " -- before mixin -- "
puts App.new.base_method

App.send(:include, ThemeMixin)

puts " -- after mixin -- "
puts App.new.base_method
puts App.new.base_method_original
puts App.new.base_method_themed

App.remove_mixin(ThemeMixin)

puts " -- after removal -- "
puts App.new.base_method
puts App.new.base_method_original
puts App.new.base_method_themed