In the documentation it is indicated, that cardinality() function is deprecated and should no longer be used. However, it is still used in the libraries such as ThermoSysPro.
e.g.
if (cardinality(C) == 0) then
some code
end if;
where C is FluidInlet or FluidOutlet
Could anyone give a simple example of how it could be replaced?
The usual solution is to make the connector conditional, and if enabled you require that it is connected.
For physical connectors you can see how heatports and support is handled in:
Modelica.Electrical.Analog.Interfaces.ConditionalHeatPort
Modelica.Mechanics.Rotational.Interfaces.PartialElementaryOneFlangeAndSupport2
For control signals you can see how p_in, h_in etc are handled in
Modelica.Fluid.Sources.Boundary_pT
Modelica.Fluid.Sources.Boundary_ph
However, the connectors of ThermoSysPro belong in neither of those categories and that should ideally also be cleaned up.