Problems with calling functions in the externalmedica library in modelica

Question

Since calling functions in the externalmedia library is slightly complicated, I created a function to call directly, but the following warning appears.

Public component state.eta was neither input nor output
in function user.pT.h_pT.
Component context: state.eta
Component declared as DynamicViscosity eta in Modelica.Media.Interfaces.Types
File: C:/Users/Yao/Desktop/ExternalMedia/Media/BaseClasses/ExternalTwoPhaseMedium.mo, line 49

The following illustration is an example of a function.

model sss
 parameter Real h1=3000;
 parameter Real T=600;
 Real p1;
equation 
    h1*1000=user.pT.h_pT(
    p1,
    T,
    0);
end sss;

function h_pT 
    extends Modelica.Icons.Function;
    input user.total.Medium.AbsolutePressure p "Pressure";
    input user.total.Medium.Temperature T "Temperature";
    input user.total.Medium.FixedPhase  phase = 0
    "2 for two-phase, 1 for one-phase, 0 if not known";
     user.total.Medium.ThermodynamicState state;
    output user.total.Medium.SpecificEnthalpy h;

algorithm 
 state:= user.total.Medium.setState_pT(
        p,
        T,
        phase);
     h:=state.h;
end h_pT;

function total

package Medium
extends ExternalMedia.Media.CoolPropMedium(
    mediumName = "Water");
end Medium;

end total;

I don't know how to solve these problems and would very much like your answer.

Answer 1

As indicated by the error message the solution is to make state protected:

function h_pT 
    extends Modelica.Icons.Function;
    input user.total.Medium.AbsolutePressure p "Pressure";
    input user.total.Medium.Temperature T "Temperature";
    input user.total.Medium.FixedPhase  phase = 0
    "2 for two-phase, 1 for one-phase, 0 if not known";
  protected
     user.total.Medium.ThermodynamicState state;
  public
    output user.total.Medium.SpecificEnthalpy h;

algorithm 
 state:= user.total.Medium.setState_pT(
        p,
        T,
        phase);
     h:=state.h;
end h_pT;