Re: [Vala] help with java to vala

["marcin saepia net" <marcin saepia net>]

What exactly do you want to achieve by making it const?


m.

2012/10/26 Calvin Walton <calvin walton kepstin ca>:
> On Thu, 2012-10-25 at 13:00 -0700, bsquared wrote:
> > I attempted a simple test using this:
> > 8< ------------------------------------------------
> >       private static const Set<string> STATIC_SET;
> >       static construct {
> >               STATIC_SET = new HashSet<string> ();
> >               STATIC_SET.add ("Hello");
> >               STATIC_SET.add ("World");
> >       }
> > ------------------------------------------------ >8
> >
> > with this result:
> > 8< ------------------------------------------------
> > valac --pkg gee-1.0 hello_set.vala
> > hello_set.vala:5.4-5.47: error: `Gee.Set<string>' not supported as type
> > for constants
> >       private static const Set<string> STATIC_SET;
> >       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> > hello_set.vala:8.3-8.16: error: The name `add' does not exist in the
> > context of `HelloTest.STATIC_SET'
> >               STATIC_SET.add("Hello");
> >               ^^^^^^^^^^^^^^
> > hello_set.vala:9.3-9.16: error: The name `add' does not exist in the
> > context of `HelloTest.STATIC_SET'
> >               STATIC_SET.add("World");
> >               ^^^^^^^^^^^^^^
> > Compilation failed: 3 error(s), 0 warning(s)
> > ------------------------------------------------ >8
> >
> >
> > To my untrained eye this appears to indicate that I cannot use these as
> > constants.  If I drop 'const' from the declaration it compiles and runs
> > correctly.
>
> This is the expected result - if the Set is constant, then you can't
> call the add method on it. It looks like the Gee Set type simply doesn't
> support being used as a constant.
>
> I think that the only types that you can actually use as constants in
> Vala are ones that compile to basic/simple C types, and therefore could
> be created using constant C initializers. If you have to write data to
> the object at run-time to fill it, it's not a compile-time constant,
> after all.
>
> This limits you to using things like arrays of structures, for example.
>
> If you really want a run-time initialized Set, then it will have to be
> non-const.
>
> --
> Calvin Walton <calvin walton kepstin ca>
>
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