Refining the .idl file for a class is typically an iterative process. For example, after running the IDL source file through the SOM Compiler and writing some code in the implementation template file, the class implementer realizes that the IDL class interface needs another method or attribute, a method needs a different parameter, or any such changes.

As mentioned earlier, the SOM Compiler (when run using the c or xc emitter) assists in this development by reprocessing the .idl file and making incremental updates to the current implementation file. This modify-and-update process may in fact be repeated several times before the class declaration becomes final. Importantly, these updates do not disturb existing code for the method procedures. Included in the incremental update are these changes:

• Stub procedures are inserted into the implementation file for any new methods added to the .idl file.

• New comments in the .idl file are transferred to the implementation file, reformatted appropriately.

• If the interface to a method has changed, a new method procedure prototype is placed in the implementation file. As a precaution, however, the old prototype is also preserved within comments. The body of the method procedure is left untouched (as are the method procedures for all methods).

• Similarly left intact are preprocessor directives, data declarations, constant declarations, non-method functions, and additional comments-in essence, everything else in the implementation file.

Some changes to the .idl file are not reflected automatically in the implementation file after an incremental update. The class implementer must manually edit the implementation file after changes such as these in the .idl file:

• Changing the name of a class or a method.

• Changing the parents of a class (see also "If you change the parents of a class..." later in this topic).

• Changing a functionprefix class modifier statement.

• Changing the content of a passthru statement directed to the implementation (.c, .C, or cpp) file. As previously emphasized, however, passthru statements are primarily recommended only for placing #include statements in a binding file (.ih, xih, .h, or .xh file) used as a header file in the implementation file or in a client program.

• If the class implementer has placed "forward declarations" of the method procedures in the implementation file, those are not updated. Updates occur only for method prototypes that are part of the method procedures themselves.