Dear swig users,
I have a C++ class that is wrapped into a Python shadow class. In
addition to regular Python input (say, a number), I would like to
allow users to pass None from the user interface and tells the C++
class no invalid input is given. It is more or less like using -1 as a
default parameter when only positive numbers are allowed.
However, SWIG does not seem to allow such usage because it will not
pass None to the C++ class even if it accepts such an input (e.g. with
a constructor that accepts a PyObject * object). Whenever I pass None,
I would get an error message such as "Invalid null reference".
When I read the wrapper file, I find the following piece of code:
if (obj5) {
res6 = SWIG_ConvertPtr(obj5, &argp6, SWIGTYPE_p_simuPOP__uintList,
0 | SWIG_POINTER_IMPLICIT_CONV);
if (!SWIG_IsOK(res6)) {
SWIG_exception_fail(SWIG_ArgError(res6), "in method '"
"new_stat" "', argument " "6"" of type '" "simuPOP::uintList const
&""'");
}
if (!argp6) {
SWIG_exception_fail(SWIG_ValueError, "invalid null reference "
"in method '" "new_stat" "', argument " "6"" of type '"
"simuPOP::uintList const &""'");
}
arg6 = reinterpret_cast< simuPOP::uintList * >(argp6);
}
The problem is that when SWIG_ConvertPtr is called
SWIGRUNTIME int
SWIG_Python_ConvertPtrAndOwn(PyObject *obj, void **ptr, swig_type_info
*ty, int flags, int *own) {
if (!obj) return SWIG_ERROR;
if (obj == Py_None) {
if (ptr) *ptr = 0;
return SWIG_OK;
} else {
It treats Py_None directly as a special case and does not call the
implicit constructor at all.
Is there a way to get around this problem?? I guess what I need is
that SWIG passes Py_None to the constructor when flag
SWIG_POINTER_IMPLICIT_CONV is set to true.
Many thanks in advance.
Bo
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