slot-exists-p
object slot-name ⇒ generalized-boolean
object—an object.
slot-name—a symbol.
generalized-boolean—a generalized boolean.
Returns true if the object has a slot named slot-name.
defclass, defstruct
defclass [Macro] , slot-missing [Standard Generic Function]
Although no implementation is required to do so,
implementors are strongly encouraged to implement the function slot-exists-p using
the function slot-exists-p-using-class
described in the Metaobject Protocol.