Re: [Vala] wish for Type Inference working for weak local variables

[lukpank o2 pl (Łukasz Pankowski)]

Jiří Zárevúcky <zarevucky jiri gmail com> writes:

> On 08/01/2009 04:36 PM, Łukasz Pankowski wrote:
> > Hello
> >
> > According to the Vala tutorial
> >
> > "Finally Vala has a mechanism called Type Inference, whereby a local
> > variable may be defined using var instead of giving a type, so long as
> > it is unambiguous what type is meant."
> >
> > Type Interface works great for owned variables (for example in
> > declaration of variable b below) but not for weak variable (neither
> > declaration of c2 nor c3 works).
> >
> > I would prefer just "weak" (as in declaration of c2) as shorter, but
> > maybe "weak var" would be more readable/discoverable?
> >
> > What do you think about the idea?  Would this be hard to implement?
> >
> >
> > class Foo {}
> >
> > void main ()
> > {
> >      // var for short
> >      Foo a = new Foo();
> >      var b = new Foo();
> >
> >      // no `weak' for short
> >      weak Foo c1 = a;
> >      weak c2 = a;            // syntax error
> >      weak var c3 = a;                // syntax error
> > }
> >    
>
> I and Julien proposed that, but juergbi closed it as WONTFIX without
> discussion.
> Maybe if more people express their opinion, we could change his mind?
>
> See this bug: http://bugzilla.gnome.org/show_bug.cgi?id=586486

Another performance related usage of the weak variables (apart from one
you mentioned in the bug comment #3) is that properties return weak
variables so the values are copied unless assigned to the weak variable
(as in the code below) and here "weak t = a.str" shortcut would also be
convenient.


class Foo {
    public string str { get; set; }
}

void main ()
{
    Foo a = new Foo();

    // uses g_strdup to duplicate the string
    var s = a.str;
    // no duplication needed
    weak string t = a.str;
}