Consider using interface type (REDU18)
This list contains objects which can be declared and implemented as an interface type, instead of as the class type implementing the interface. The advantage is that interface reference counting can be used so you will not have to explicitly free the object.
Example:
The list will not include objects that are not created. These objects are probably just assigned to another object.
Another condition that must be met is that the object is of a class that implements exactly one interface.
See also: