objc:objc-object-var-value

(objc:objc-object-var-value object var-name &key result-pointer)

The value of the instance variable var-name, declared with (:objc-instance-vars ...) of objc:define-objc-class, converted by its type; setf writes it (an object variable takes an object pointer, which the variable does not retain). A structure value is filled into result-pointer when it is given. An object without the variable signals. Part of the macOS-only objc package -- the interpreter (java -jar, or the rontolisp native binary), a compiled .class / .jar and a --native executable for macOS on Apple silicon, never a .wasm; on a machine without the runtime it signals an error. See the macOS GUI guide.

MY-APP> (define-objc-class counter () () (:objc-class-name "Counter")
          (:objc-instance-vars ("count" :int)))
COUNTER
MY-APP> (defvar *c* (make-instance 'counter))
*C*
MY-APP> (setf (objc-object-var-value *c* "count") 17)
17
MY-APP> (objc-object-var-value *c* "count")
17