Re: Best practise inheritance

[Emmanuele Bassi <ebassi gmail com>]

On Tue, 21 Mar 2017 at 21:23, S. Jacobi <sjacobi mailueberfall de> wrote:

> On Tue, 21 Mar 2017 20:53:04 +0000
> Emmanuele Bassi <ebassi gmail com> wrote:
>
> > Also, do not store a private pointer in your instance structure, and
> > use the get_private_instance() function that the G_DEFINE_TYPE macro
> > creates for you.
> So you say whenever I need access to the objects private data I should
> call G_TYPE_INSTANCE_GET_PRIVATE, despite the mentioned overhead?

Nope. I said to use the get_instance_private() function generated for your
type by the G_DEFINE_TYPE macro, which uses pointer arithmetic and an
offset computed when the class is instantiated and it's constant for all
instances.

The GET_PRIVATE macro has to compute the offset on every invocation,
instead.

> > The GObject tutorial has a good introduction on how to define types
> > and how to use them.
> Indeed. It took me a while to walk through it. However, the example
> given in [3] has the comment /* Other members, including private data.
> */, which would contradict your opinion, or is at least a bit unclear,
> because final and derivable types are handled a bit differently.


Please, file a bug against the documentation component of the GLib product
in Bugzilla, so we can fix this and make it clearer.

Ciao,
 Emmanuele.

> [3] https://developer.gnome.org/gobject/stable/howto-gobject-code.html
>
> > Ciao,
> >  Emmanuele.
> > On Tue, 21 Mar 2017 at 19:57, Nicola Fontana <ntd entidi it> wrote:
> >
> > > the lookup indeed is quite expensive, and looking at the
> > > implementation [1] it is not that straightforward.
> > >
> > > The very same example provided by the official documentation [2]
> > > caches that pointer into the instance struct.
> > >
> > > [1] https://git.gnome.org/browse/glib/tree/gobject/gtype.c#n4709
> > > [2]
> https://developer.gnome.org/gobject/stable/gobject-Type-Information.html#g-type-class-add-private
> > >
> _______________________________________________
> gtk-app-devel-list mailing list
> gtk-app-devel-list gnome org
> https://mail.gnome.org/mailman/listinfo/gtk-app-devel-list
-- 
https://www.bassi.io
[@] ebassi [@gmail.com]