Is it possible to pass pointers to defined types in Cython to constructors,
for example:

cdef extern from "Foo.h":
    cdef cppclass Bar:
        pass

cdef class PyClass:
    cdef Bar *bar

    def __cinit__(self, Bar *b)
        bar = b

When you do this, you get a *Cannot convert Python object to 'Bar *'*.* *

(Copied from
http://stackoverflow.com/questions/12204441/passing-c-pointer-as-argu...,
the top answer there is convoluted and seems to be just wrapping a double,
what I'm trying to do is a bit more complicated)

I am using such a construct to implement a "Has-A" (composition)
relationship between two types that are defined as structs in a C Library.

In my code, the Class *Bar* has a non-trivial constructor, and the
"constructor" for *PyClass* in C should receive a pointer to an initialized
*Bar* object.

Is there a simple way of doing this?

Python class construction requires a Python call, hence Python object
arguments. The two answers given on stackoverflow (writing a global
method that constructs the object then sets the pointer, or creating a
wrapper class for Bar you an pass around in Python space) are the
typical ways of handling this. There's not really anything "simpler"
(though that's pretty simple).

- Robert

On 27.09.2012 11:39, Horace Abenga wrote:

__cinit__ takes the same arguments as __init__.

Sturla

On 27.09.2012 11:39, Horace Abenga wrote:

Uaually this is an error of reasoning, as a non-trival constructor will
be non-trivial outside __cinit__ as well. So calling it from __cinit__
cannot be more difficult than calling it from anywhere else.

Sturla

For each cdef class create a global cdef function that acts as a
constructor, CefResponse is a C++ object, PyResponse a python equivalent of
a c++ object:

   1. cdef object CreatePyResponse(CefRefPtr[CefResponse] cefResponse):
   2.  
   3.     pyResponse = PyResponse()
   4.     pyResponse.cefResponse = cefResponse
   5.     return pyResponse
   6.  
   7. cdef class PyResponse:
   8.  
   9.     cdef CefRefPtr[CefResponse] cefResponse
   10.  
   11.     def GetStatus(self):
   12.  
   13.         return (<CefResponse*>(self.cefResponse.get())).GetStatus()

Czarek.