How to pass user data using OpenCV trackbar

Currently I have a number of sliders that are used to change image values. I am using the OpenCV track bar for the slider which has a callback to a different function for each of my sliders. I would like to have my sliders callback point to a single callback function and then use the user data to identify which track bar made the call.

Here is the documentation for the track bar

I am unsure what values i should be passing to void*, and also how to then retrieve this value form my callback function Below is an example of my track bar which compiles.

int ref = 1;
createTrackbar("Name","Window",0, 1, myFunc, &ref);

In my callback function I try and retrieve the value of ref.

void myFunc(int value, void *userdata)
{
    int val = *((int*)&userdata);
    cout << val << endl;
}

I had issues trying to convert the pointer back to an int, this is a solution i found online which gives me val as the address of ref.

int val = *((int*)&userdata);

This seems a lot of hassle, as i then have to get the value back form the address at val. Is there an easier way to do this?

No, there is no simplier way. It's nessesary minimum for functionality you want.