Jiří Zárevúcky píše v Pá 05. 02. 2010 v 16:08 +0100:
> Fredderic Unpenstein píše v Pá 05. 02. 2010 v 23:57 +1100:
> > 2010/1/23 Sam Liddicott <s...@liddicott.com>:
> > > I used a language called charamel for controlling 3d figurs. It's
> > > closures supported
> > > variables in 2 ways.
> > >
> > > Like valàa reference to the instantaneous value of the variable, and
> > > fixing it's value
> > > (making a copy) at the time the closure was made.
> >
> > How WOULD you do that in present Vala...? That seems like an awfully
> > obvious thing you might want to do, to be so difficult.
> >
> > The only way to do it that I can think of, in the example above, would
> > be attach the current value of i to the button as user data. Seems
> > awfully convoluted, and not always particularly practical.
> >
>
> It is awfully simple. You don't need Vala to do it.
>
> void main () {
> for (int i = 0; i < 10; ++i) {
> int t = i;
> Idle.add (() => { print ("%d", t); return false; });
> }
>
> new MainLoop ().run ();
> }
>
> TADAAAAA! You have the value in that particular iteration fixed.
> Does anyone need something more sophisticated?
>
> So, why does this work?
> i is defined before the loop and destroyed after it's exited.
> i is the same variable in all iterations.
> t is defined inside the iteration and destroyed when the iteration ends.
> t is a different variable in every iteration.
>
> You don't need anything from Vala. The way it works is entirely logical.
>
A little better example:
void main () {
MainLoop loop = new MainLoop ();
for (int i = 0; i < 10; ++i) {
int t = i;
Idle.add (() => { print ("i: %d\n", i); return false; });
Idle.add (() => { print ("t: %d\n", t); return false; });
}
Idle.add (() => { loop.quit(); return false; });
loop.run ();
}
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