dolfin team mailing list archive

["Martin Sandve Alnæs" <martinal@xxxxxxxxx>]

2008/8/23 Garth N. Wells <gnw20@xxxxxxxxx>:
>
>
> Martin Sandve Alnæs wrote:
>>
>> Add an instantiation of Array<DirichletBC*> to the .i files beside
>> ArrayFunctionPtr.
>
> I added this.
>
>> An use cpp_DirichletBC.
>
> I tried this is demo/pde/sym-dirichlet-bc/python/demo.py, but I get
>
> Traceback (most recent call last):
>  File "demo.py", line 55, in <module>
>    bc = cpp_DirichletBC(u0, mesh, boundary)
> NameError: name 'cpp_DirichletBC' is not defined

from dolfin.dolfin import cpp_DirichletBC

Note that cpp_DirichletBC won't hold on to python referenced objects,
so you need to keep some python references to your meshfunctions
and vectors etc. to avoid garbage collection.

> As you say, this is a problem with this
>>
>> "inheritance pattern".
>>
>
> Is there a way to 'up cast' Python objects. For example, DirichletBC is
> derived from cpp_DirichletBC, so can I get a cast a DirichletBC object to a
> cpp_DirichletBC object?
>
> Garth

The DirichletBC object is already a cpp_DirichletBC object, it obviously
works fine for single objects, so the problem is in the vector typemap.
Maybe you can create an empty ArrayDirichletBC() and add one item
at a time to it?

a = ArrayDirichletBC()
for b in bcs:
    a.push_back(b)

--
Martin