The "universal" Method

 

As described in section 5.2.1 GRAPE searches for a method "universal" if the method that is send to an instance is neither found in the instance's class nor in its superclasses. If the method

   GRAPE(inst, "universal")(method)

INSTANCE * inst
char * method

is found, it is send to the instance with the method method that was originally called as parameter. If you supply an "universal" method for a class the method method can for example be passed on to one of the instance variables of the instance inst.

Be careful: only parameterless methods can be called via universal, any argument passed to the original method is lost. Therefore if the method method needs parameters on the class it is send to this won't work. Because the GRAPE function doesn't know if a method needs parameters it will always try to use "universal" if the original method wasn't found.

The behaviour of the GRAPE function can be influenced by calling one of the methods

     

INSTANCE/CLASS * obj

"unset-universal-send" switches the universal mode off, "set-universal-send" switches it on again (by default it is on). Be careful when switching universal mode off, many classes like Scene, TimeScene and Time_Object rely on this mechanism.