HP Integrity NonStop J-Series - Manual (Page 223)

lexicographically in a case sensitive manner. See class RWCString in the Class Reference for
details.
Object Destruction
All objects inheriting from class RWCollectable inherit a virtual destructor. Hence, the actual type
of the object need not be known until run time in order to delete the object. This allows all items in
a collection to be deleted without knowing their actual type.
As with any C++ class, objects inheriting from RWCollectable may need a destructor to release the
resources they hold. In the case of Bus, the names of passengers and customers are
RWCollectableString s that were allocated off the heap. Hence, they must be reclaimed. Because
these strings never appear outside the scope of the class, we do not have to worry about the user
having access to them. Hence, we can confidentially delete them in the destructor, knowing that no
dangling pointers will be left.
Furthermore, because the set pointed to by customers_ is a superset of the set pointed to by
passengers_, it is essential that we delete only the contents of customers_.
Here's a possible definition:
Bus::~Bus()
{ customers_.clearAndDestroy();
delete passengers_;
}
Note that the language guarantees that it is okay to call delete on the pointer passengers_ even if it
is nil.
How to Add Polymorphic Persistence
The saveGuts() and restoreGuts() virtual functions are responsible for saving and restoring the
internal state of
RWCollectable objects. To add persistence to your RWCollectable class, you must
override the saveGuts() and restoreGuts() virtual member functions so that they write out all of
your object's member data. The next two sections describe approaches you can use to correctly
define these functions.
Multiply Referenced Objects describes how these functions handle
multiply-referenced objects.
Polymorphically saving an object to a file may require some knowledge of the number of bytes that
need to be allocated for storage of an object. The binaryStoreSize() function calculates this value.
Virtual Function binaryStoreSize() describes how to use binaryStoreSize().
RWCollection has its own versions of the saveGuts() and restoreGuts() functions that are used to
polymorphically save collections that inherit from that class. Polymorphically Persisting Custom
Collections briefly describes how these functions work.
Virtual Functions saveGuts(RWFile&) and saveGuts(RWvostream&)