Re: [Boost-users] [python] nested attributes, style question

From: David Abrahams (dave_at_[hidden])
Date: 2005-12-13 18:11:09

Malte Clasen <news_at_[hidden]> writes:

> Hi,
>
> let's say we've got the following C++ classes:
>
> class position {
> public:
>      float get_height() const;
>      void set_height(float value);
> private:
>      float height_;
> };
>
> class object {
> public:
>      position get_position() const;
>      void set_position(const position& value);
> private:
>      position pos_;
> };
>
> This design is not fixed, but right now this is the starting point. When 
> I added the boost.python interface to it using add_property(), I quickly 
> noticed that using these classes feels somehow unpythonic: I cannot 
> modify the height of the position of an object using
>
>      obj.pos.height = x
>
> because get_position() returns the position by value, so the following 
> set_height modifies a temporary instance of position. The work-around on 
> the python side looks clumsy:
>
> Is there a common solution to this problem? Does my proxy approach seem 
> reasonable?

http://thread.gmane.org/gmane.comp.python.c++/8966 should help.  Use
return_internal_reference.

-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com