Re: Cast Object - get null

[Jakob Ovrum]

On Wednesday, 18 April 2012 at 17:28:16 UTC, Jonathan M Davis 
wrote:
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

T opCast(T : const(Vector2D!U), U)() const
{
    return new T(x, y);
}