When an Objective-C class is implemented in Lisp, each Objective-C foreign object has an associated Lisp object that can obtained by the function objc-object-from-pointer. Conversely, the function objc-object-pointer can be used to obtain a pointer to the foreign object from it associated Lisp object.
There are two kinds of Objective-C foreign object, classes and instances, each of which is associated with a Lisp object of some class as described in the following table:
subclass of standard-objc-object
The implementation of an Objective-C class in Lisp consists of a subclass of standard-objc-object and method definitions that become the Objective-C methods of the Objective-C class.
LispWorks Objective-C and Cocoa Interface User Guide and Reference Manual - 15 Dec 2011