[C++-sig] Lifetime of Python object for a pointer argument

[Min Xu]

On Sat, 2002-02-16 at 11:14, Achim Domma wrote:
> Hi,
> 
> I'm also not an expert, so hopefully Dave will correct my if I'm wrong. As
> far as I know it's in general not an good idea to pass objekts as pointers
> in the current version of boost.python, so you should prefer passing
> parameters by value.
According to the document section on pointers and smart pointers, the
const ptr* as an argument is handled automatically. 

An return value of type const ptr* does work in this code. See

>>> g=grid()
>>> a=geometry (g)
>>> b=a.getGrid ()
>>> del a
>>> b.a()
1.0 	# Expected. b has a separate life from a as the copy constructor is
used in b=a.getGrid()

> 
> > // C++ part
> > class grid
> > {
> > public:
> >    grid() { ... }
> >    ...
> > };
> 
> Do you allocate dynamic memory in grid ? If yes, is the copy-constructor
> implemented ?
> 
The grid class does not dynamic allocate memory and the copy constructor
is implemented. 

The simplified class of grid is like this:

class grid
{
public: 
	grid() : _a(1) {...}
	grid(double a, ...) : _a(a) {...}
        grid(const grid& g) {...}
	double a() const { return _a; }
private:
	double _a;
};

> greetings
> Achim
Thanks.

> 
> 
> 
> 
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