[cjc96]

Hey!
As always, I hope everyone is keeping well at the moment!

I'm still stumbling my way through self-teaching C++ and basic OpenFOAM editing/development but without the time available to properly devote to learning C++ explicitly, I'm basically building my knowledge one error at a time.

Last week I implemented a new functionObject bringing the DESModelRegions functionality from OpenFOAM v2.3 to OpenFOAM v7 with a little help from wyldckat's own implementation but using a slightly different structure as a practice exercise.

The function itself works but I've had to implement a small workaround to overcome a compilation error. The problem section is as follows:

{
	const icoDESmodel& DES = dynamic_cast<const icoDESmodel&>(turbModel);

	tmp<volScalarField> tDESfield(DES.LESRegion());
	volScalarField &DESmodelRegions = tDESfield.ref();

	word result("DESmodelRegions");

	return store
	(
		result,
		DESmodelRegions / dimensionedScalar(dimless, 1)
	);
}

Without the (mathematically) redundant division by one, the compiler complains about type mismatches, specifically:

error: no matching function for call to ‘Foam::functionObjects::DESmodelRegions::store(Foam::word&, Foam::volScalarField&)’

‘Foam::volScalarField {aka Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh>}’ is not derived from ‘const Foam::tmp<T>’

Now, I know enough to infer that the issue is if I just attempt to store 'DESmodelRegions' the program is trying to store a word, whereas with the division by one, it's being forced into storing a volScalarField as is intended. So I think the problem is in improper use of referncing in my actual calculation of DESmodelRegions, but I don't know what I've actually done wrong and arbitrary removal/addition of references didn't accomplish much

Obviously the current implementation works but is far from elegant and I'd like to understand how to avoid it in the future, so if anyone could point out my error I'd be very grateful as always!

[olesen]

Originally Posted by cjc96

Without the (mathematically) redundant division by one, the compiler complains about type mismatches, specifically:

error: no matching function for call to ‘Foam::functionObjects::DESmodelRegions::store(Foam::word&, Foam::volScalarField&)’

‘Foam::volScalarField {aka Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh>}’ is not derived from ‘const Foam::tmp<T>’

Now, I know enough to infer that the issue is if I just attempt to store 'DESmodelRegions' the program is trying to store a word, whereas with the division by one, it's being forced into storing a volScalarField as is intended.

Actually the problem the error shows is not the word (first parameter) but the second parameter! The store() expects the second parameter to be tmp type, which it can claim the memory of etc. In your version that didn't compile, you passed a volScalarField for storage, not a tmp. By adding in the pointless division operation, you have created a tmp and it works. You will have to decide yourself which quantity you want to store.