On Wednesday, April 18, 2012 19:15:21 Namespace wrote:
> > one another, you're going to need to overload opCast.
> >
> > - Jonathan M Davis
>
> Thanks for your answer.
> I have tried to overload opCast in this way:
> U opCast(U)() const {
> return U(this.x, this.y);
> }
>
> But then i get this compiler error
> cast.d(36): Error: no property 'opCall' for type 'object.Object'
> cast.d(299): Error: template instance
> cast.Vector2D!(short).Vector2D.opCast!(Obj
> ect) error instantiating
> cast.d(36): Error: no property 'opCall' for type 'object.Object'
> cast.d(299): Error: template instance
> cast.Vector2D!(float).Vector2D.opCast!(Obj
> ect) error instantiating
>
> The dokumentation of opCast is very short, did i understand
> opCast wrong?
You're dealing with a class, so you need to use new. As it stands, you're
trying to call an overload static opCall on U, and presumably, you haven't
declared one.
Ideally, you'd also have a template constraint restricting the cast to the
types that you want to be able to cast to, but since you're dealing with a
templated type, that can be a bit tricky. One (somewhat ugly) option would be
to do something like
U opCast(U) const
if(is(Unqual!U == Vector2D!byte) ||
is(Unqual!U == Vector2D!ubyte) ||
is(Unqual!U == Vector2D!short) ||
is(Unqual!U == Vector2D!ushort) ||
is(Unqual!U == Vector2D!int) ||
is(Unqual!U == Vector2D!uint) ||
is(Unqual!U == Vector2D!long) ||
is(Unqual!U == Vector2D!ulong) ||
is(Unqual!U == Vector2D!float) ||
is(Unqual!U == Vector2D!double) ||
is(Unqual!U == Vector2D!real))
{
return new U(x, y);
}
Another would be to have an enum on the type indicating that it's an
instantiation of your Vector2D template (e.g. isVector2D).
U opCast(U) const
if(__traits(compiles, U.isVector2D))
{
return new U(x, y);
}
- Jonathan M Davis
