TreeNode_MethodMissing.rb

class TreeNode
  def method_missing(methodname, *args, &block)
    child = self.children().find { |child| methodname.to_s == child.name }
    if child.nil?
      child = TreeNode.new(methodname.to_s)
      self.add_child(child)
    end
    child.instance_eval(&block) if block_given?
    child
  end
end