Objective-C defines its own memory management, so most interaction with its objects occurs using foreign pointers with the FLI type descriptor objc-object-pointer. When an Objective-C object class is implemented in Lisp, there is an additional object of type standard-objc-object which is associated with the foreign pointer (see Defining Objective-C classes and methods).
There are a few specific Objective-C pointer types that have a direct translation to FLI types:
Other pointer types are represented using the
FLI type descriptor as normal.
When using pointers to struct types, the type must be defined using define-objc-struct rather than
LispWorks Objective-C and Cocoa Interface User Guide and Reference Manual - 15 Dec 2011