Re: [Vala] Access the "klass" parameter of a class_init() function in vala with "static construct"

[Evan Nemerson <evan coeus-group com>]

On Sat, 2010-07-31 at 22:08 +0200, Sébastien Wilmet wrote:
> 2010/7/31 Evan Nemerson <evan coeus-group com>
>         On Sat, 2010-07-31 at 17:59 +0200, Sébastien Wilmet wrote:
>         > Hello!
>         >
>         > What I want to do is to implement a GtkAction derived class
>         which sets
>         > GtkActionClass:toolbar_item_type to
>         GTK_TYPE_MENU_TOOL_BUTTON in its
>         > class_init function.
>         
>         
>         Vala doesn't currently expose *Class structs in the bindings,
>         so AFAIK
>         what you're talking about can't be done easily. I'm not
>         exactly an
>         expert on GObject, but I think you should be able to hack
>         something
>         together by going creating bindings for GtkActionClass then
>         getting
>         access to it with GLib.Object.get_class. This is untested, but
>         you
>         should get the idea:
>         
>         
>         /* In a vapi */
>         [Compact, CCode (cname = "GtkActionClass")]
>         public class GtkActionClass {
>          public GLib.Type menu_item_type;
>          public GLib.Type toolbar_item_type;
>         }
>         
>         /* Your code */
>         unowned GtkActionClass ac = (GtkActionClass) this.get_class
>         ();
>         ac.toolbar_item_type = typeof (MenuToolButton);
>         
>
> I have this error:
> error: Access to instance member `GLib.Object.get_class' denied

You aren't going to be able to access it from a static construct block.
Try it from within a regular construct block.

> Also, in C the cast can be made because the first field in a Class
> struct is the parent class.

That doesn't really solve anything, since you don't have access to the
instance from within a static constructor (hence the error about access
to an *instance member* being denied). Whether you just cast or use the
G_OBJECT_CLASS macro, you still need an instance.


-Evan