Using Caché Objects - InterSystems Documentation

Using Callback Methods
20.6 %OnDelete
This class method is called by the %Delete method just before an object is deleted. This
method can be used to ensure that deleting an object does corrupt data integrity, such as by
ensuring that an object designed to contain other objects is only deleted when it is empty.
Its syntax is:
ReturnValue %OnDelete(OID AS %ObjectIdentity)
where:
ReturnValue
OID
A %Status code, where an error code stops the deletion.
An object identifier for the object being deleted.
This method is available to the %Library.Persistent class and its subclasses.
20.7 %OnDetermineClass
This class method is called by the %Delete, %Oid, and %Open methods when one of these
receives a partially-formed OID as an argument. The purpose of %OnDetermineClass is to
supply a class name to its calling method.
Its syntax is:
ReturnValue %OnDetermineClass(OID As %ObjectIdentity, ByRef Class As
%String)
where:
ReturnValue
OID
Class
A %Status code, where behavior depends on the calling routine. If
invoked by %Open, the attempt to open the object fails, no OREF is
returned, and the error status is passed back to the caller. If invoked
by %Delete, the attempt to delete the object fails.
The instance with the partially-formed name
A string in which the name of the instance's class is placed.
This method is available to the %Library.Persistent class and its subclasses.
174 Using Caché Objects