title: Example of a rails custom formbuilder for a radiobutton list
body: <p>I am looking for an example of how to create a custom form builder for a radio button list bound to an object that acts_as_tree.  I already have the code that displays the radio button list but want to DRY it up by refactoring into a formbuilder.  I can't find any examples of a custom form builder for radio button lists.</p>
  
  <p>Any pointers/links would be appreciated.</p>