_LINKING USER INFTERFACE AND DATABASE OBJECTS_
by Eng-Lee Kwang and Christopher Rosebrugh

EXAMPLE 1: 

(a) 

    /* message template description */
    %func_template bool UI_DO_SOMETHING_M (
        obj_id                            /* IN:  object pointer  */
    );

   /* Object class message description mapping. It is NOT necessary to declare 
     * parameters to message since they are already defined in template. */
    %function[UI_DO_SOMETHING_M]  ui_Bag_do_something;

--------------------------------------------------------------------------
(b)

/* These macros are used by the UI framework to pass messages to particular
* objects without requiring explicit knowledge of the object classes.
* The typedef and macros are AUTOMATICALLY generated from the message 
* template description.  These macros, etc. are only used by framework. */
#define UI_DO_SOMETHING_M_ID     1
typedef void                     (*UI_DO_SOMETHING_M_fn_t)( obj_id  );
#define UI_DO_SOMETHING_M(_ftbl) (*(UI_DO_SOMETHING_M_fn_t)_ftbl[UI_DO_SOMETHING_M_ID])

/* Messages are implemented as re-directed MACRO'ed functions through function 
 * table. This typedef and define is AUTOMATICALLY generated from a high-level
 * message description. */
    typedef void  (*ui_Bag_do_something_fn_t)( obj_id  );
    #define ui_Bag_do_something (*(ui_Bag_do_something_fn_t)bag_ftbl[1])

/* Message function table for object class Bag. This table is AUTOMATICALLY 
 * generated from the high-level message description. */
    void *bag_ftbl[19] = {
        (void *)...,
        (void *)_ui_Bag_do_something,
        ...
    };


EXAMPLE 2:

(a)

    void _ui_Bag_do_something(
        ui_Bag_t  *bag                  /* corresponds to an obj_id */
        )
    {
        ....
    }


(b)

/* Implementation of messaging mechanism for sending message DO_SOMETHING */
    bool ui_do_something(
        obj_id    id, 
        ...
        )
    {
        void  **ftbl;
    
        /* look for message function table associated with the object ID. */
        ftbl = __find_object_ftbl(id);
        if (ftbl && &UI_DO_SOMETHING_M(ftbl)) {
           /* If function table exists for the object -> known object type
            * and message DO_SOMETHING is defined, pass the message to the
            * object (call the function!!) */
           return UI_DO_SOMETHING_M(ftbl)(id, ...);
        }
        return FALSE;
    }



EXAMPLE 3:

   db_handle = db_Int16_new(123);

   viewer_1 = ui_Num_new(...);

   viewer_2 = ui_Gauge_new(...);

   ui_attach_data(viewer_1, db_handle);

   ui_attach_data(viewer_2, db_handle);