[raumpolizei]

Hey everyone,
I found something interesting that I wanted to discuss before reporting it as a bug (?). In the thermophysicalModels library, more precisely in the psiThermo class, there is the following function:

Foam::tmp<Foam::volScalarField> Foam::psiThermo::mu() const
{
    return mu_; // mu_ is psiThermo member
}

I was wondering why the shared Foam::tmp is used here. The combination of the function with the GeometricField:perator= makes it possible to steal mu from the class and I don't think that this is what was intended. So basically, I cannot assign an lvalue to thermo.mu() because after the assignment the mu_ is now in an undefined state. This can be tested like this:

// thermo is of type psiThermo
 //muSteal has been initialzed
muSteal = thermo.mu();
Info << "muSteal[0] = " << muSteal[0] << nl;
Info << "thermo.mu()()[0] = "<<thermo.mu()()[0] << nl;

Note that using thermo.mu() as temporary is fine, like this because now we are taking the field from the temporary:

 //muCopy has been initialzed
 muCopy= dimensionedScalar("zero",dimless,1.)*thermo.mu();
Info << "muCopy[0] = " << muCopy[0] << nl;
Info << "thermo.mu()()[0] = "<<thermo.mu()()[0] << nl;

So what do you think about this guys? I would suggest returning a const reference instead to make the encapsulation more complete:

const Foam::volScalarField& Foam::psiThermo::mu() const
{
    return mu_;
}

Thanks for taking a look!
Cheers RP