> 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.
