set brightness ios10.9

//CGDisplayIOServicePort is depreciated in OS 10.9 – so you have to use IOServiceGetMatchingServices to get the service parameter for IODisplaySetFloatParameter.

- (void) setBrightnessTo: (float) level
{

    io_iterator_t iterator;
    kern_return_t result = IOServiceGetMatchingServices(kIOMasterPortDefault,
                                                        IOServiceMatching("IODisplayConnect"),
                                                        &iterator);

    // If we were successful
    if (result == kIOReturnSuccess)
    {
        io_object_t service;
        while ((service = IOIteratorNext(iterator))) {
            IODisplaySetFloatParameter(service, kNilOptions, CFSTR(kIODisplayBrightnessKey), level);

            // Let the object go
            IOObjectRelease(service);

            return;
        }
    }
}