Add userdata example

[rdwnsjjd]

Hi.
your userdata was unused. but I want to use it and pass some data to the handlers.
How to init userdata?

[janfari]

Hi,
userdata takes a void pointer. You should be able to create a pointer to your data, cast it to void and pass it through then cast it to the correct pointer type in your handler. For example I believe something like this will work (there may be typos, this is untested)

int my_data = 3;

r = sd_bus_call_async(bus, NULL, m, my_callback, (void*) &my_data, 1);

And in the handler

static int my_callback(sd_bus_message *m, void *userdata, sd_bus_error *ret_error) {
        if *(int *) userdata > 5
        {
                // Do something
         }
        return 0;
}

I'll test and add some examples to the code when I can.