Hi Zim!

The correct use of onBeforeWrite is:

http://doc.silverstripe.org/doku.php?id=datamodel#onbeforewrite

You can use it in your News_Page.php, something like this:

class News_Page extends Page {
   
   public static $db = array(
"IsMainStory" => "Boolean"
   );
   
   public static $has_one = array(
   );

function onBeforeWrite() {
if( $this->IsMainStory )
//IsMainStory is checked
else
//IsMainStory is not checked
parent::onBeforeWrite();

}
   
}

class News_Page_Controller extends Page_Controller {
public function init() {
      parent::init();
   }
}

I think this could run fine. Try it.

Good luck!

.. in fact it would be in the first bit? am i on the right lines?

function onBeforeWrite() {

if( $this->IsMainStory )

//IsMainStory is checked so uncheck it before checking new one?

IsMainStory=false //is this the right syntax?

else

parent::onBeforeWrite();

}

The onBeforeWrite method is only called on the DataObject that is about to be saved. It won't be called on all other pages automatically, so you have to take care of that yourself. Your problem can easily be solved with an SQL query.. here's an example code:

I assumed, that you have a table with a the same name as your Class in the DB (NewsPage?). If yes, the provided code should work out of the box. If that's not the case, find out in which table the IsMainStory field is stored and fill in the table name here:

Got it working with this

function onBeforeWrite() {
   
      
    // check if MainStory is true
    if( $this->IsMainStory ){
       // if yes, make sure no other story is main-story
       // we use a raw sql query here to set all IsMainStory to 0
       DB::query('UPDATE ' . $this->ClassName . ' SET IsMainStory=0');
      
       DB::query('UPDATE ' . $this . ' SET IsMainStory=1 WHERE ID=' . $this->ID);

    }
   
    // call parent first
    parent::onBeforeWrite();
   
   }

Thanks for your help people