Added the final version of the Mac OS X delegate type code.

delegatetypes_darwin.go

@@ -0,0 +1,49 @@
+// 27 february 2014
+package main
+
+import (
+	"fmt"
+	"unsafe"
+)
+
+// #cgo LDFLAGS: -lobjc -framework Foundation
+// #include <stdlib.h>
+// #include "objc_darwin.h"
+// /* because cgo doesn't like Nil */
+// Class NilClass = Nil;
+import "C"
+
+var (
+	_NSObject_Class = C.object_getClass(_NSObject)
+)
+
+func newDelegateClass(name string) (C.Class, error) {
+	cname := C.CString(name)
+	defer C.free(unsafe.Pointer(cname))
+
+	c := C.objc_allocateClassPair(_NSObject_Class, cname, 0)
+	if c == C.NilClass {
+		return fmt.Errorf("unable to create Objective-C class %s; reason unknown", name)
+	}
+	C.objc_registerClassPair(c)
+	return c, nil
+}
+
+// according to errors spit out by cgo, C function pointers are unsafe.Pointer
+func addDelegateMethod(class C.Class, sel C.SEL, imp unsafe.Pointer) error {
+	// maps to void (*)(id, SEL, id)
+	ty := []C.char{'v', '@', ':', '@', 0}
+
+	// clas methods get stored in the metaclass; the objc_allocateClassPair() docs say this will work
+	// metaclass := C.object_getClass(C.id(unsafe.Pointer(class)))
+	// we're adding instance methods, so just class will do
+	ok := C.class_addMethod(class,
+		sel,
+		C.IMP(imp),
+		&ty[0])
+	if ok == C.BOOL(C.NO) {
+		// TODO get function name
+		return fmt.Errorf("unable to add selector %v/imp %v (reason unknown)", sel, imp)
+	}
+	return nil
+}