Re: [Vala] Creating constructors on binded classes

[Jürg Billeter <j bitron ch>]

On Sat, 2007-09-15 at 07:29 +0100, Alberto Ruiz wrote:
> I have the following class from clutter:
>
>     [CCode (copy_function = "clutter_knot_copy", cheader_filename =
> "clutter/clutter.h")]
>     public class Knot : GLib.Boxed {
>         public int x; 
>         public int y;
>         public weak Clutter.Knot copy ();
>         public bool equal (Clutter.Knot knot_b);
>         public static GLib.Type get_type ();
>     }
>
> I don't really know why is it a class, since the structure 

Yes, it should probably be a struct, you should change that.

> Obviously, in Vala, we want something more natural and comfortable
> than:
> var knot = new Knot();
> knot.x = 1;
> knot.y = 2;
>
> Since usually, you have collections of several knots, in C you see the
> use of this class as: 
> Knot[] knots = {{1, 2}, {3, 4}, {5, 6} ...}
>
> I would like to, at least, provide a simple constructor:
> var knots = new Knot[] { new Knot(1, 2), new Knot(3, 4), ...}

It should be a bit better with the new object initializers. For example:
(untested)

Knot[] knots = new Knot[] { new Knot() {x=1, y=2}, ... };

> The problem here is that if I create a new function, I need to copy
> paste the whole class, hide it in metadata, paste it on
> clutter-0.4-custom.vala and implement the new constructor. I don't
> quite like this idea, is it possible to just add the constructor in
> the custom file without getting the error that Knot is already
> defined? 

Vala bindings currently don't allow any custom code at all, they are all
compile-time only (and without real code injection). I don't know yet
whether we want to add limited support for actual code in Vala bindings.
You can add a helper/factory method for creating Knot instances to your
application, of course.

Jürg