Magic type return

[Andrea Fontana]

Yes I did it using Variant and it works fine

Il giorno mer, 18/07/2012 alle 16.42 +0200, Philippe Sigaud ha scritto:

> > class Known
> > {
> >          void* data; // external data by c api
> >          int type;  // 0 for int, 1 for string, etc. ..
> > }
> >
> > How can I implement a method like this?
> >
> > Known  known;  // <-- suppose known.type == 1;
> > string s  = known.value(); // <-- automatic 
> >
> > I just know how to do this:
> >
> > string s = know.value!string(); 
> 
> As bearophile said, you cannot change a value's type (which is a
> compile-time construct) with a runtime value, as is Known.type. 
> 
> Second point, in D, the rhs is fully evaluated before being assigned
> to the lhs, I think. So, known.value() must evaluate to *something*,
> without knowing it will be assigned to a string.
> In your example, what happens if known.type != 1? 
> 
> You can use Phobos Variant, (or Algebraic if the range of types you
> plan to use is known beforehand). Then, you should test typeid before
> using it.
> 


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