Date: 2001-01-19 15:39:18
I am using the latest CVS snapshot of boost.
We are trying to define BPL Python bindings for some C++ classes that
we are developing. In particular, we have a container class that
manages a set of a polymorphic objects. I have distilled the idea down
to a relatively simple example, dynatype.cpp. This file is available
the boost egroup upload area:
This simple python script shows what we want to do:
# Container with variables of a polymorphic type.
c = dynatype.container() # <container object at 1400523a0>
# Possible type identifiers are 'int' or 'double'.
# Get references to the variables in the container.
i = c.get('an_int') # <dynavalue_int object at 1400523f0>
d = c.get('a_double') # <dynavalue_double object at 140052440>
# Change the values of the variables.
# Get them back (as Python integer or float).
i.get() # 3
d.get() # 3.1415
# This proves that j.set() changes the contents of the container.
j = c.get('an_int') # <dynavalue_int object at 1400523f0>
j.get() # 3
i.get() # 4
This actually works, but there are a few issues:
0. Note that the values in the container are based on an abstract
C++ class "dynabase."
The actual values are C++ objects of the type "dynavalue<int>"
The container is implemented using a
std::map<string, boost::shared_ptr<dynabase> >
1. The Python c.get() is bound to the C++ function py_get().
Somewhere inside this function we have to have a dynamic_cast<>()
from a shared_ptr<dynabase>
to a shared_ptr<dynavalue<int> >
or a shared_ptr<dynavalue<double> >.
To do this, I had to modifiy smart_ptr.hpp (line 139):
shared_ptr(const shared_ptr<Y>& r) : px(dynamic_cast<T*>(r.px))
++*(pn = r.pn);
1. Is there a better way of doing this?
2. If not, would there be a way of having both the old and my
modified copy constructor, and could this become part of
the standard smart_ptr.hpp?
2. There is a horrible memory leak associated with the use of c.get().
I am pretty sure that this is due to the following invocation of
boost::shared_ptr<dynavalue<int> > dvi(dv);
What is wrong with this use of to_python()?
Any advice is very much appreciated!
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