Type Templates

Boilerplate macros for type operations.

At the top of the file for most libGimbal derived types, along with the type identifier, you will find a collection of convenience utility macros implementing function-style casts for the given type.

// type UUID macro (expands to GblObject_type() registration function)
#define GBL_OBJECT_TYPE                     (GBL_TYPEID(GblObject))
 
// instance function-style cast macro
#define GBL_OBJECT(instance)                (GBL_CAST(instance, GblObject))
 
// class cast function-style cast macro
#define GBL_OBJECT_CLASS(klass)             (GBL_CLASS_CAST(klass, GblObject))
 
// instance-to-class cast macro
#define GBL_OBJECT_GET_CLASS(instance)      (GBL_CLASSOF(instance, GblObject))

While these macros are obviously optional, they do add a lot to the codebase in terms of readability and convenience as well as uniform styling. With these sorts of macros defined, we then gain access to lots of convenience:

// create a floating object class
//    - easy cast to particular class
GblObjectClass* pClass  = GBL_OBJECT_CLASS(GblClass_createFloating(GBL_OBJECT_TYPE));
 
// lets override just its implementation of the GblIEventHandlerClass interface
//    - easy cast to particular interface
GblIEventHandlerClass* pIEvent = GBL_IEVENT_HANDLER_CLASS(pClass);
// override virtual method
pIEvent->pFnEvent = [&](GblIEventHandler* pSelf, GblEvent* pEvent) {
     // easy cast to particular instance type
     GblObject* pSelfObj = GBL_OBJECT(pSelf);
 
     printf("%s received an Event!", GblObject_name(pSelfObj));
 
 
     if(GBL_TYPECHECK(pEvent, MyEventType)) {
         // easy cast to particular event instance
         MyCustomEvent* pEvent = MY_CUSTOM_EVENT(pEvent);
 
         // do something
     } else if(GBL_TYPECHECK(pEvent, MyOtherEventType)) {
         // easy cast to particular event instance
         SomeOtherEvent* pEvent = SOME_OTHER_EVENT(pEvent);
 
         // do something
     }
}
 
GblObject* pObject = GblObject_createWithClass(pClass);
// easy cast from object to GblInstance base
GblInstance_sinkClass(GBL_INSTANCE(pObject));
// easy cast from object to GblBox base
GblBox_unref(GBL_BOX(pObject));