Emulating Python class variables in C++
Hi there,
I am porting a Python library to C++ - and re-exposing back to Python
with boost (suffice to say the Python API is fixed).
I am having problems emulating class variables from boost as C++ static
data members using inheritance. Here's an example:
using namespace boost::python;
using namespace std;
struct A {
static string value;
};
struct B : public A {
static string value;
};
string A::value("A");
string B::value("B");
BOOST_PYTHON_MODULE(test)
{
class_<A>("A")
.def_readonly("value", &A::value);
class_<B>("B")
.def_readonly("value", &B::value);
}
If I don't specify inheritance using bases<>, then this works. But I
need inheritance, so I write:
BOOST_PYTHON_MODULE(test)
{
class_<A>("A")
.def_readonly("value", &A::value);
class_
On 2/08/2015 20:05, Will Hall wrote:
struct A { static string value; };
struct B : public A { static string value; };
string A::value("A"); string B::value("B");
While I can't answer your question directly, I can tell you that this is bad coding practice in C++. Usually it stems from a misunderstanding, while other times it's just a bad design.
So, to summarise, any idea how to provide polymorphic Python class variables in boost::python?
Static/class fields cannot be polymorphic, by definition.
On August 2, 2015 8:41:08 PM EDT, Gavin Lambert
On 2/08/2015 20:05, Will Hall wrote:
struct A { static string value; };
struct B : public A { static string value; };
string A::value("A"); string B::value("B");
While I can't answer your question directly, I can tell you that this is bad coding practice in C++. Usually it stems from a misunderstanding, while other times it's just a bad design.
Have you considered type traits. Don't know how that works with python though. template<class T> struct policy { static const bool value = false; }; struct policy<A> { static const bool value = true; }; There's an interesting tutorial here: http://www.cantrip.org/traits.html
So, to summarise, any idea how to provide polymorphic Python class variables in boost::python?
Static/class fields cannot be polymorphic, by definition.
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participants (3)
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Gavin Lambert -
Michael -
Will Hall