Strategy_pattern + extend self

strategy_pattern_extend_self.rb

# http://en.wikipedia.org/wiki/Strategy_pattern + extend self

module StrategyA
  extend self

  def execute
    puts 'Doing the task the normal way'
  end
end

module StrategyB
  def execute
    puts 'Doing the task alternatively'
  end
end

module StrategyC
  def execute
    puts 'Doing the task even more alternatively'
  end
end

module ProxyExt
  extend self

  def define_extension(extension)
    case extension
    when :rghost
      StrategyA
    when :prawn
      StrategyB
    else
      extension
    end
  end
end

class Context
  include ProxyExt
  extend ProxyExt
  extend define_extension(:rghost)

  def initialize(strategy=nil)
    self.class.send :include, define_extension(strategy)
  end

end

Context.execute
a = Context.new(:rghost)
a.execute #=> Doing the task the normal way

b = Context.new(StrategyB)
b.execute #=> Doing the task alternatively

c = Context.new(StrategyC)
c.execute #=> Doing the task even more alternatively