[C++-sig] make_constructor issues

Ralf W. Grosse-Kunstleve rwgk at yahoo.com
Fri Jul 23 21:38:26 CEST 2004

--- Stefan Seefeld <sseefeld at art.ca> wrote:
> hi there,
> the wrapper 'python.hpp' header doesn't include
> the 'make_constructor.hpp' file. Shouldn't it ?
> Then I try to make
> Foo make_foo()
> {
>   Foo foo;
>   foo.init();
>   return foo;
> }
> a constructor (i.e. binding it to '__init__' via
> 'make_constructor'), but I get an error message about
> 'element_type' not being a member of Foo. The
> examples I'v found all use pointes, so I changed
> the 'make_foo' function to return a pointer.
> That works, but is not what I want to do.

Why not? It is just a technical detail that you have to adjust to. I.e. you
could to this (untested):

 shared_ptr<Foo> make_foo()
   Foo foo;
   return shared_ptr<Foo>(new Foo(foo));

But this requires that Foo is copy-constructable and you incur a
runtime-penalty for executing the copy constructor. I'd generally prefer this:

 shared_ptr<Foo> make_foo()
   shared_ptr<Foo> foo_ptr(new Foo);
   Foo& foo = *foo_ptr;
   return foo_ptr;

Is this approach impractical in your environment? If so, what are the reasons?


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