Hi,

I'm trying to create a new dataobject called Category. You can have categories and sub-categories so I'm trying to code it so that a Category object can have another Category object as it's parent (has_one) or it can have multiple "Category" objects (has_many).

I thought this would be quite simple but I can't work out how to get around this error (see title of post). This is what I have so far:

class Category extends DataObject { 
	static $db = array(
		'Name' => 'Text',		
		"Type" => "Enum('Business, Event, Community', 'Business')"		
  );
	static $default_sort = "Name";

  static $has_one = array(	
    'Parent' => 'Category'
  );
	static $has_many = array(
		'Children' => 'Category'
	);
 
	function getCMSFields_forPopup() {
		$fields = new FieldSet();
		$fields->push( new TextField( 'Name' ) );		
		$fields->push( new DropdownField("ParentID", "Parent Category", array()));		
		$fields->push( new DropdownField("Type", "Type", 
			array(
				'Business' => 'Business',
				'Event' => 'Event',
				'Community' => 'Community'
			)
		));		
		return $fields;
	} 
}

I can see that it's not happy with the field I'm trying to create where you select the parent Category (or leave empty if it's a top-level category). How do I do this?? Are there any examples I can look at in one of the modules? I looked at the Post object in the Forum module but it's slightly different.

Thanks.