hash_picker.rb

class Hash
  class Mediator < BasicObject
    def initialize(hash, *syms)
      @h = hash
      @syms = syms
    end

    def method_missing(name, *args)
      @h.has_key?(name) ? @h[name] : super
    end

    def mediate(&block)
      instance_eval(&block)
    end
  end

  def pick(*syms, &block)
    Mediator.new(self, *syms).mediate(&block)
  end
end