AddCallback with args?

[cinekqw1]

Hello guys,

I want to use ObservableGauge as a metric for my class.
I need to create observable gauges in real time, for example in some vector. great!
The problem I am facing is how can I push some args into calleble method which allow me to distinguish what observable object was called?
Once I pass same callable method I am not able to distinguish what object is called.

Example code:
`void foo_library::observable_counter_example(const std::string &name)
{

std::string counter_name = name + "_observable_counter";
auto provider = metrics_api::Provider::GetMeterProvider();
nostd::shared_ptr<metrics_api::Meter> meter = provider->GetMeter(name, "1.2.0");
double_observable_counter = meter->CreateDoubleObservableCounter(counter_name);
double_observable_counter->AddCallback(MeasurementFetcher::Fetcher, nullptr);
}`
In above example you can define some static Fetcher method but you cant pass any args. Maybe this nullptr is ptr to args?
in documentation this ptr is called *state which nothing says to me.

Any idea?