处理未定义的变量

<%= render \'video\', :video => @video, :video_id => \'video_show_id\' %>

<% if video_id %>
  <%= link_to \"video\", video.video_url, :class => \"oembed\", :id => video_id %>
<% else %>
  <%= link_to \"video\", video.video_url, :class => \"oembed\" %>
<% end %>

:video_id

:video_id => \"\"

defined?

<% if defined? video_id %>

module VideoHelper 

  def show_video(video, options = {})
    options[:id] ||= \"\"
    render \'video\', :video => video, :video_id => options[:id]
  end  

end

<% if defined? video_id %>