Re: [boost] help

From: David Abrahams (dave_at_[hidden])
Date: 2002-11-12 14:32:48

¿ÂÃÍ <k.meng_at_[hidden]> writes:

> Hi:
>
> I  have a question, if my base class has a clone pure virtual function,what can I do to write
> the wrap class?
>
>    struct Base
>     {
>         virtual int f() = 0;
>         virtual Base* clone() = 0;
>     };
>
>     struct BaseWrap : Base
>     {
>         BaseWrap(PyObject* self_)
>             : self(self_) {}
>         int f() { return call_method<int>(self, "f"); }
>         Base* clone(){ return call_method<Base*>(self, "clone");}
>         PyObject* self;
>     };
>
> If I write it like this,it report compile error.

There's nothing wrong with the class declarations shown above, in and
of themeselves. They compile just fine for me.

However, I doubt you want the clone method you've got there. What will
happen, assuming your derived Python class creates a new object in its
clone() override, is that the Python object which holds your BaseWrap
object will have only a single reference count, and to avoid returning
you a dangling pointer, call_method<> will raise a Python exception.

We're currently investigating ways to make your BaseWrap class be /the
same as/ the wrapping Python object, so that their lifetimes will
always be tied together. We hope to have a solution later this week.

-- 
                       David Abrahams
   dave_at_[hidden] * http://www.boost-consulting.com
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