Release 10.1A: OpenEdge Getting Started:
Object-oriented Programming

Compiling class files

A class is a user-defined data type and encompasses all classes and interfaces above it in its hierarchy. When you compile a class, the compiler does not only compile the .cls file identified to the compiler. Instead the compiler compiles all the .cls files that compose its hierarchy. For each class file that is in the class's hierarchy, the compiler generates in-memory r-code and if the compiler SAVE option is specified, generates an r-code file.

Thus, the files compiled by the compiler include:

The requested class file.
Class files for the super classes in the class hierarchy.
Class files for any implemented interfaces for this class.
Class files for any implemented interfaces for classes in the class hierarchy.
Any include files that the class and interface files use.

The compiler does not fully compile or generate an r-code file for referenced class files, that is, other classes that are instantiated within a class using the NEW statement. The compiler instead inspects referenced class files to determine their external interfaces (their public methods and data members). This information is used to validate the use of these classes in the class being compiled. The compiler traces up through the referenced class's hierarchy for super classes and interfaces. It does not check any additional class references specified in this referenced class hierarchy.

Caution: When you compile a class, although Progress automatically compiles all super classes in its class hierarchy, it does not know about and cannot automatically compile any of the subclasses of the class you are compiling. Thus, when you change a super class, you must compile the class and all subclasses of the class to ensure that all objects with this class in their hierarchy inherit the updated state or behavior. Progress, by itself, has no knowledge of these subclasses, so you must keep track of them manually or by using configuration management tools.