Re: [Vala] Generating bindings for non-GLib/GObject based API

[Michael Wild <themiwi users sourceforge net>]

On 22. Apr, 2010, at 20:43 , Jan Hudec wrote:

> On Thu, Apr 22, 2010 at 11:47:21 +0200, Michael Wild wrote:
> > 1) Constructor function: Say I would like to use a C function as the
> > constructor for a class (as e.g. newwin is used in curses.vapi). However,
> > that C function does not return the allocated and initialized object in the
> > return value, but as the first argument. The return value is an error code
> > instead. How would I handle this?
>
> I believe you'll have to declare it as a static function and wrap it as
> constructor in the .vapi itself.
>
> I suppose you have a function like:
>
> int thing_init(Thing **self, int param);
>
> (allocate+return by reference implies pointer-to-pointer, right?)
>
> Than in the class you first declare the function itself, like
>
> class Thing {
>    private static init(out Thing self, int param);
>
> Than you need to define the constructor, which is where I am a bit lost.
> It does work for normal methods, but constructor is a bit special.
> I would guess this might work:
>
>    public Thing(int param) throws ThingError {
>       int status = init(this, param);
>       if(status != 0)
>           throw new ThingError.FAILED(
>               "Thing construction failed with status %d", status);
>    }
>
> But I am not sure whether you need to initialize this or create normal
> variable and return it or employ some other trick. Maybe defining another
> static function and than rebinding it as constructor. Something like
>
>    public static Thing new(int param) throws ThingError {
>       Thing self;
>       int status = init(self, param);
>       ...
>       return self;
>    }
>    public Thing(int param) throws (ThingError);
>
> You'll have to play with it a bit.
>
> Note, that I made it throw an error. I assume if it returns an error code,
> you'll want to get it somehow and since the allocated object is the return
> value, an exception is the only option.

Thanks, I was stumbling along the same lines. However, now I'm stuck because I can't convince Vala to 
generate the C-code for the static functions in the .vapi file.


Michael