How to define a ValueHash?

Question

I try to define a ValueHash similar to the ValueList example in the Vala tutorial:

[Compact]
public class ValueHash : HashTable<string, Value?> {
    [CCode (has_construct_function = false)]
    protected ValueHash ();
}

Compiling this with valac 0.22 yields an

error: unable to chain up to base constructor requiring arguments
protected ValueHash ();

Searching the net I figured a call to the bas() constructor is needed, but how? Trying out (I know that null is not a valid argument here):

protected ValueHash () { base(null, null); }

yields:

error: too few arguments to function ‘g_hash_table_new_full’
protected ValueHash () { base(null, null); }

OK, probably need one argument more?

protected ValueHash () { base(null, null, null); }

yields:

error: Too many arguments, method `GLib.HashTable<string,GLib.Value?>'
does not take 3 arguments
protected ValueHash () { base(null, null, null); }

I cannot figure out what's going on here. As gobject already defines a ValueArray in the GLib namespace, a ValueHash would come in handy there, but incidentally this looks to be defined in libsoup-2.4, but I don't want to introduce a dependency on libsoup in my code.

Thanks for any hints.

Answer 1

I'm not sure if there is a way to chain up to the 2-parameter constructor (or if what you are seeing is really a bug) but I believe calling the 4-parameter version explicitly works in any case:

[Compact]
public class ValueHash : HashTable<string, Value?> {
    [CCode (has_construct_function = false)]
    protected ValueHash () {
        base.full (str_hash, str_equal, null, null);
    }
}