问如何在Swift中使用AXObserverAddNotification？

EN

    func observe(app:pid_t, element:AXUIElement) {
        var observer: AXObserver? = nil
        func callBack(observer: AXObserver?, element: AXUIElement?, notification: CFString, refcon: UnsafeMutableRawPointer?) {
            print("Fired! \(notification)")
        }
        if AXObserverCreate(app, callBack, &observer) == .success {
            print("AXObserverCreate success!")
            if AXObserverAddNotification(observer!, element, kAXMainWindowChangedNotification as CFString, UnsafeMutableRawPointer(Unmanaged.passRetained(self).toOpaque())) == .success {
                print("AXObserverAddNotification success!")
                CFRunLoopAddSource(CFRunLoopGetCurrent(), AXObserverGetRunLoopSource(observer!), .defaultMode)
                print("Watching \(element.value(of:"AXTitle"))")
            }
        }
    }