objc:define-objc-block-type

(objc:define-objc-block-type name result-type (argument-type*))

Names a block signature: name then stands for (result-type (argument-type*)) in objc:make-objc-block, objc:with-objc-block and objc:call-objc-block. The types are the ones objc:invoke's list form takes, checked here. Answers name; needs no runtime. 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-block-type comparator :long-long
          (objc-object-pointer objc-object-pointer))
COMPARATOR
MY-APP> (with-objc-block (compare 'comparator
                                  (lambda (a b)
                                    (let ((x (ns-string-to-string a))
                                          (y (ns-string-to-string b)))
                                      (cond ((string< x y) -1) ((string> x y) 1) (t 0)))))
          (invoke-into '(array string) *words* "sortedArrayUsingComparator:" compare))
#("apple" "fig" "pear")