Xml and habtm associations

Hi, I am building an app in rails and i’m having some trouble in passing a model object to xml.
The model name is event and it habtm videos, I’d like to pass the event information (name, date, description) as well the videos(link, title, duration) information to xml.

With the code below i was able to pass only the event information to xml, but not the videos.
def show
@event = Event.find_by_id(params[:id])
respond_to do |format|
format.html # show.html.erb

  format.xml { render :xml => @event }

end
end

I was hoping to avoid writing rxml files… but if it is not possible someone can plz pass me a tutorial about it

Thx in advance