Delete Rule
The options in the Delete Rule section specify what to do
when the source object of a relationship is deleted. There are four
options:
- Nullify disassociates
all destination objects from the source object by removing references
to them. So, when an Agent object is deleted, its related Customer
objects are not deleted but the Customer objects’ references to
Agent are nullified (the entry in the join table is set to
null). - Cascade deletes all objects that are
the destination of a relationship whose source is deleted. So, when
an Agent object is deleted, all of its related Customer objects
are also deleted.
- Deny refuses the deletion if a source
object has any destination objects. So, if an Agent object has any
Customer objects, deleting the Agent object is denied. In order
for the deletion of the Agent object to succeed, its destination
objects (Customer objects) must either be deleted or changed to
something other than destination objects of the Agent object.
- No Action deletes the destination object
but does not remove any back references to the source object. So,
if a Customer object is deleted, its reference to its Agent object
is not removed. Using this option may result in dangling references
in the data source.
© 2002 Apple Computer, Inc. (Last Updated November 2002)