A object of type standard-objc-object.
A foreign pointer or
objc-object-var-value returns the value of the instance variable var-name in the Objective-C foreign object associated with object. The type of value depends on the declared type of the instance variable. If this type is a foreign structure type, then the result-pointer argument should be passed giving a pointer to a foreign object of the correct type that is filled with the value.
Note that it is only possible to access instance variables that are defined in Lisp by define-objc-class, not those inherited from superclasses implemented in Objective-C.
LispWorks Objective-C and Cocoa Interface User Guide and Reference Manual - 21 Mar 2017