The next.wo.DisplayGroupDelegate interface defines methods that the DisplayGroup's delegate should implement. To define a delegate for DisplayGroup, have your object conform to this interface and use DisplayGroup's setDelegate method to set the delegate to be your object.
The DisplayGroup invokes delegate methods when performing several of its major functions. For example, DisplayGroup's updateDisplayedObjects filters the objects fetched from the database using a qualifier and sort ordering. However, if the DisplayGroup has a delegate and the delegate implements displayArrayForObjects, it invokes this method instead. The delegate is then responsible for filtering the objects and returning a sorted array.
The DisplayGroup sends the delegate messages when it has fetched, created an object (or failed to create one), inserted or deleted an object, changed the selection, or set a value for a property. It also sends messages that request permission from the delegate to perform most of these same actions. The delegate can return true to permit the action or false to deny it.