[snip]
>>>
>>> Function should not change the FunctionSpace (that's why FunctionSpace is
>>> const). FunctionSpace shouldn't depend on the data and its size should be
>>> defined when creating the FunctionSpace.
>>
>> The same applies for FunctionSpace as its member variables are private
>> and the public accessors are read-only which. Consider a sub-class
>> ImageFunctionSpace:FunctionSpace, with a constructor like:
>>
>> ImageFunctionSpace(ImageType *imagePtr)
>>
>> where imagePtr is supposed to initialise FunctionSpace::_mesh using
>> the image size, and then _dofmaps itself is initialised using _mesh.
>> How would you do that considering the restrictions?
>>
>
> The FunctionSpace has pointers to the mesh, etc. You just need to create
> your mesh and pass it to the FunctionSpace constructor. What else you then
> do with the mesh, etc is up to you.
That can be done _outside_ of a sub-class. A sub-class of
FunctionSpace doesn't have a control over _mesh of its own parent
FunctionSpace. The following example may make this more clear:
template <typename TImage>
class DolfinImageFunctionSpace : public dolfin::FunctionSpace
{
public:
// just some itk typedefs -- ignore
typedef TImage ImageType;
typedef typename ImageType::PixelType PixelType;
typedef typename ImageType::SizeType SizeType;
// .. and some dolfin typedefs -- ignore
typedef typename std::tr1::shared_ptr<const dolfin::Mesh>
MeshConstPointerType;
typedef typename std::tr1::shared_ptr<const dolfin::FiniteElement>
ElementConstPointerType;
typedef typename std::tr1::shared_ptr<const dolfin::DofMap>
DofMapConstPointerType;
// the ctor
DolfinImageFunctionSpace(ImageType* imageData,
MeshConstPointerType mesh,
ElementConstPointerType element,
DofMapConstPointerType dofmap) :
dolfin::FunctionSpace(mesh, element, dofmap)
{
SizeType imageSize = imageData->GetBufferedRegion().GetSize();
// here, we whish to call some thing like:
// _mesh = UnitSquare(imageSize[0], imageSize[1]);
// but it's private and the accessor is read-only.
};
}
-Ali
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