19.0 Guide/Application Classes

Database frozen objects (R)

The advent of ObjectStore necessitates storing some of our classes into application databases. These classes have restrictions to the changes that are allowed without requiring a schema update to existing customer databases.

Programmers may add or remove virtual methods, but may not add the first nor delete the last virtual method. Doing so will cause the creation or deletion of the vtable, resulting in a schema update.

Programmers may not change the type or order of data members of these frozen classes.

The list of frozen classes can be found in the file obschema.cc in the obDesign area. Part of this list includes TAttribute, TAttributeSet, TString, TProperty, specLine, multiSpecLine, attribute reference classes, and Poi derivatives.

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