Using Caché Objects - InterSystems Documentation

RemoveProjection
The RemoveProjection method is a class method that is invoked when either 1) a
class definition is deleted or 2) at the start of a recompilation of the class. This method
is passed the name of the class being removed, an array containing the parameter
values (subscripted by parameter name) defined for the projection, and a flag indicating
whether the method is being called as part of a recompilation or because the class
definition is being deleted.
When a class definition containing a projection is compiled the following events occur:
1. If the class has been compiled previously, it will be “uncompiled” before the new
compile begins (that is, all the results of the previous compilation are removed). At this
time, the compiler invokes the RemoveProjection method for every projection with a
flag indicating that a recompilation is about to occur.
Note that you cannot call methods of the associated class from within the
RemoveProjection method as the class will not exist at this point.
Also note that if you add a new projection definition to a class that had been previously
compiled (without the projection) then the compiler will call the RemoveProjection
method on the next compilation even though the CreateProjection method has never
been called. Implementors of the RemoveProjection method have to plan for this possibility.
2. After the class is completely compiled (i.e., it is ready for use), the compiler will invoke
the CreateProjection method for every projection.
When a class definition is deleted, the RemoveProjection method is invoked for every projection
with a flag indicating that a deletion has occurred.
16.2.2 The Standard Projection Classes
Projection Classes
In order to easily provide additional services (such as Java support) Caché provides the following
projection classes as part of its standard class library:
Using Caché Objects 143