Adding a Class to the System

 

Together with the methods described in section 5.4.2 the following methods provide the basic operations for handling classes and methods in an object-oriented environment. All these basic methods belong to class Root, therefore they can be invoked on every class via inheritance.

To create a new class call

   (CLASS * ) GRAPE(superclass, "new-class")(name, size)

CLASS * superclass
char * name
int size

This will create a subclass of superclass named name. For every new instance of this class size bytes of memory will be allocated, therefore size should be the size of the struct of the new class (sizeof(NAME)). The result of this method is a pointer of type CLASS * to the new class. This value should be stored in a class pointer CLASS *Name, see section 5.3.2 for naming conventions.

Classes can be deleted by calling

   GRAPE(My_Class, "delete")()

CLASS * My_Class

The class My_Class will be removed from the class hierarchy only if there are neither subclasses nor instances of My_Class left.

All "delete" methods should return NULL, then the return value of the "delete" call can be used to reset the pointer to the instance or class that was deleted:

obj = (MY_CLASS *)GRAPE(obj, "delete")();

To check if a class with a specific name exists the method

   (CLASS * ) GRAPE(class, "find-class")(name)

CLASS * class
char * name

can be used. It will search all subclasses of class class for a class named name and return the pointer to that class or NULL if no class with that name exists.