Re: How do I create an object instance from a tag?

["Randy Brukardt" <randy@rrsoftware.com>]

"Grein, Christoph"<christoph.grein@eurocopter.com> wrote:
>
>So there are good reasons why there is not yet a solution for this
problem.


The main one is discriminants. Tagged type discriminants never have
defaults. Moreover, you can add discriminants to any extension of a
tagged type, so you never can know if you have any. And, certainly, the
creation of an object with uninitialized discriminants is a no-no.

What you really want to do is force the calling of a particular
constructor function. (That's what T'Class'Input does, after all, with
T'Input being the constructor).

If you have a dispatching constructor "Make", then you want something
like:

    Obj : T'Class := T.Make (<params>) using <tag object>;

But the reviewers thought that special syntax was overkill for this
problem, and no one has been able to come up with any other solution
that really works.

      Randy.