Hey,
My problem is the following:
I do have a C++ class, "BaseClass", that I am extending in Python
("SubClass"). Also there is another C++ class, let's call it
"BaseClassManager" which has a vector of BaseClass* (well, actually it's
holding shared_ptr's). Instances of "SubClass" are created in Python,
but ownership has been transferred to C++, as "BaseClassManager" holds
all the objects.
Here is the code that illustrates this:
Wrapped BaseClassManager
------------------------------------
class_<BaseClassManager>("GameBaseX")
.def("addObject", &BaseClassManager::addObject) // takes
shared_ptr< BaseClass>&
.def("getObjectByName",
&BaseClassManager::getObjectByName); // takes a string, returns
shared_ptr<BaseClass>
WrapperClass for Base (needed for transferring ownership)
------------------------------------
class BaseClassWrap : public BaseClass{
public:
BaseClassWrap( PyObject* self_, const std::string& name)
: BaseClass(name),self(self_) { Py_INCREF(self); }
BaseClassWrap( PyObject* self_, const BaseClass& copy ) :
BaseClass(copy), self(self_) { Py_INCREF(self); }
~BaseClassWrap() { Py_DECREF(self); }
PyObject *self;
};
Wrapped BaseClass
------------------------------------
class_<BaseClass, shared_ptr<BaseClassWrap> >("BaseClass",
init<const std::string&>())
.add_property("name", make_function(&BaseClass::getName,
return_value_policy<copy_const_reference>()) );
// both needed for using shared_ptr's together with the wrapper-class
register_ptr_to_python<shared_ptr<BaseClass> >(); // to_python converter
implicitly_convertible<shared_ptr<BaseClassWrap>, shared_ptr<BaseClass> >();
Subclass
------------------------------------
class Subclass(BaseClass):
def __init__(self, name):
BaseClass.__init__(self, name)
self.foo = "bar"
------------------------------------------------------------------------------
Imagine the following Python code:
obj = SubClass("superclass")
BaseClassManager.addObject(obj)
# and somewhere else
obj = BaseClassManager.getObjectByName("superclass")
print obj.name # prints "superclass" as expected
print obj.foo # AttributeError: 'BaseClass' object has no
attribute 'foo'
Seems all attributes got lost, be it a member-variable or methods I
defined in SubClass. Strangely obj is in both cases the same pointer (f.
ex. "SubClass object at 0x02343345").
Is there something I can do to preserve the attributes? Otherwise it is
kind of senseless to extend a C++ class in Python if it can't have its
own attributes.
Thanks a lot for the help.
Cheers.
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