slot-unbound class instance slot-name ⇒ {result}*
| class | the class of the instance. |
| instance | the instance in which an attempt was made to read the unbound slot. |
| slot-name | the name of the unbound slot. |
| result | an object. |
The generic function slot-unbound is called when an unbound slot is read in an instance whose metaclass is standard-class. The default method signals an error
of type unbound-slot. The name slot of the unbound-slot condition is initialized to the name of the offending variable, and the instance slot of the unbound-slot condition is initialized to the offending instance.
The generic function slot-unbound is not intended to be called by programmers. Programmers may write methods for it. The function slot-unbound is called only indirectly by slot-value.
If slot-unbound returns, only the primary value will be used by the caller, and all other values will be ignored.
The default method on slot-unbound signals an error of type unbound-slot.
An unbound slot may occur if no :initform form was
specified for the slot and the slot value has not been set,
or if slot-makunbound has been called on the slot.