Using Caché Objects - InterSystems Documentation

Using Callback Methods
Since different types of classes support different events, not all callback methods are available
to all classes. For example, callback methods triggered by saving or deleting an object cannot
be accessed by registered objects since these objects cannot be saved or deleted.
With the exception of %OnDetermineClass, these methods can be used to perform any
processing desired at the relevant event.
%OnDetermineClass is a special case. When %Open or %Delete is given a partially-formed
OID, it calls the %OnDetermineClass method, if the user has provided one, to obtain the
actual class name. If %OnDetermineClass indicates the object belongs to a different class,
%Open or %Delete will dispatch to the new class' %Open or %Delete method. If there is
no %OnDetermineClass method, %Open and %Delete simply assume the current class is
the correct class.
20.1 %OnAddToSaveSet
This instance method is called by the %AddToSaveSet method. The %AddToSaveSet
method itself is called on an object whose %Save method has been invoked, as well as all
other objects referenced by that object that have been loaded into memory. %AddToSaveSet
can also be invoked directly from %OnAddToSaveSet. If %OnAddToSaveSet modifies
another object, then it is the responsibility of %OnAddToSaveSet to invoke %AddToSaveSet
on that modified object.
When you invoke %Save on an object, called, for example, MyPerson, Caché generates a
list of objects that MyPerson references. A SaveSet is the list of objects consisting of the
object to be saved and all the objects that it references. In the example, the SaveSet might
include referenced objects MySpouse, MyDoctor, and so on.
The syntax of %OnAddToSaveSet is:
ReturnValue %OnAddToSaveSet(SaveDepth As %Integer, Insert As %Integer,
CallCount As %Integer)
where:
170 Using Caché Objects