C++ nested class name cannot be accessed

[Wei Wu]

According to the documentation
(http://docs.cython.org/src/userguide/wrapping_CPlusPlus.html#nested-class-declarations),
Cyhon support wrapped c++ declaration (and the idea of native c++
support is really cool). But I found that the inner class name can be
accessed only if the outer class is defined with template.

Here is an example:

a.h
------
template<typename T>
class A
{
public:
class B
{};
};

class C
{
public:
class B
{};
};

test.pyx
---------
cdef extern from "a.h":
cdef cppclass A[T]:
cppclass B:
pass

cdef cppclass C:
cpplcass B:
pass

def main():
cdef A[int].B a_b # ok
cdef C.B c_b # error: 'C' is not a cimported module

I thought the way of accessing the name of nested class was using '.'
compared to c++'s '::', and the 'C.B' above was interpreted as getting
attribute of a module.
Or am I doing something wrong here?

[Robert Bradshaw]

Looks like a bug (or not implemented feature) in C++ support.
http://trac.cython.org/cython_trac/ticket/659

- Robert

[klo...@gmail.com]

I just ran into this problem. Looks like the bug has not been fixed yet. Any suggested workarounds?

Cheers,
kloffy

[Robert Bradshaw]

On Sat, Jul 11, 2015 at 6:55 AM, <klo...@gmail.com> wrote:
> I just ran into this problem. Looks like the bug has not been fixed yet. Any
> suggested workarounds?

Are you trying to do something different than
https://github.com/cython/cython/blob/master/tests/run/cpp_nested_classes.pyx
?

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[klo...@gmail.com]

On Sunday, July 12, 2015 at 10:38:17 AM UTC+10, Robert Bradshaw wrote:

On Sat, Jul 11, 2015 at 6:55 AM,  <klo...@gmail.com> wrote:
> I just ran into this problem. Looks like the bug has not been fixed yet. Any
> suggested workarounds?

Are you trying to do something different than
https://github.com/cython/cython/blob/master/tests/run/cpp_nested_classes.pyx
?

 

Yes, the difference is that the external declaration is in a separate pxd file.

cimport cpp_nested_classes_support

cdef cpp_nested_classes_support.A.B b

Then you get the "'cpp_nested_classes_support.A' is not a cimported module" error.
 
Which gave me an idea:

from cpp_nested_classes_support cimport A

cdef A.B b

And sure enough that works, so that's my workaround for now, I guess.