Copier classes

In many cases, PolicyCenter uses a copier as well as a matcher. For example, jobs other than submission jobs need to do the following process, which is known as DuplicateAdd.

Generate a policy difference between two branches to find added entity instances.
Use matchers to check whether new entity instances have a match elsewhere in the graph.
If a match exists, use copiers to ensure that the matches are fully synchronized, as defined by the entity type.

A copier class is able to completely duplicate an entity instance.

Important: If you write a new matching class, you must write a new copier class. If a copier class does not exist or does not correctly implement the duplication of the entity instance, a task such as a DuplicateAdd does not work as expected. PolicyCenter might extend an existing entity, but lose new property values by not copying them.

In a typical policy difference operation, the difference generation is read-only. The difference generation itself does not need to copy data from one entity to a duplicate of that entity.

Each entity type that uses a copier class extends that class from the abstract class gw.api.copy.Copier or one of its subclasses. For example, the copier class for the PersonalAuto entity type is PersonalVehicleCopier.

If you create a new entity type that the policy graph uses, you need to create a copier class for that entity type. Similarly, if you extend an existing entity, you must determine whether that extension affects the copier class. If your extension includes a database-backed property, you typically need to copy that property. For example, if you extend the PersonalAuto entity type, consider whether you need to modify the PersonalVehicleCopier class.