def validate_single_association(reflection)
        association = association_instance_get(reflection.name)
        record      = association && association.reader
        association_valid?(reflection, record) if record
      end
def validate_single_association(reflection)
        association = association_instance_get(reflection.name)
        record      = association && association.reader
        association_valid?(reflection, record) if record
      end
Validate the association if <tt>:validate</tt> or <tt>:autosave</tt> is
 turned on for the association.