An example using method_missing to add user features

features.rb

require 'set'

class User
  def initialize
    @features = Set.new
  end

  def method_missing(meth, *args)
    if meth.to_s =~ /^can_(.*)\?$/
      @features.include? $1.to_s
    elsif meth.to_s =~ /^can_(.*)$/
      @features << $1.to_s
      self
    else
      super
    end
  end
  
  def respond_to?(meth)
    if meth.to_s =~ /^can_(.*)\?$/
      true
    elsif meth.to_s =~ /^can_(.*)$/
      true
    else
      super
    end
  end
end

u = User.new
u.can_code
puts u.can_code?