objc:ns-error-object
(objc:ns-error-object condition)
The NSError an objc:ns-error carries, an objc:objc-object-pointer holding one reference (released when the pointer is collected). A reader of a condition of the macOS-only objc package; see the macOS GUI guide.
MY-APP> (defvar *e* (handler-case (invoke-with-error (invoke "NSFileManager" "defaultManager")
"attributesOfItemAtPath:error:" "/no/such/file")
(ns-error (e) e)))
*E*
MY-APP> (invoke-into 'string (ns-error-object *e*) "domain")
"NSCocoaErrorDomain"