Using Caché Objects - InterSystems Documentation

16
Class Projections
Class projections provide a way to extend the behavior of the Caché Class Compiler. A class
projection associates a class definition with a projection class. A projection class (derived
from the %Projection.AbstractProjection class) provides methods that are invoked by the Class
Compiler when it compiles and removes a class definition.
Projection classes are used by Caché to automatically generate additional code when a class
is compiled as well as perform needed cleanup when a class is deleted. The projection
mechanism is used by the Java, EJB, and C++ projections (hence the origin of the term
“projection” ) to automatically generate the necessary client binding code (Java or C++)
whenever a class is compiled.
16.1 Projection Definitions
Every class definition may optionally include one or more projection definitions. Each definition
has a unique name and specifies the projection class to be used for the projection as
well as parameter values that are passed to the projection methods (allowing each projection
to have customized behavior).
16.1.1 Adding a Projection to a Class
You can associate a projection with a class by adding a projection definition to its class definition.
In Caché Studio you can do this using the Projection statement within a class definition:
Using Caché Objects 141