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Yes I did it using Variant and it works fine<BR>
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Il giorno mer, 18/07/2012 alle 16.42 +0200, Philippe Sigaud ha scritto:<BR>
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> class Known<BR>
> {<BR>
> void* data; // external data by c api<BR>
> int type; // 0 for int, 1 for string, etc. ..<BR>
> }<BR>
><BR>
> How can I implement a method like this?<BR>
><BR>
> Known known; // <-- suppose known.type == 1;<BR>
> string s = known.value(); // <-- automatic <BR>
><BR>
> I just know how to do this:<BR>
><BR>
> string s = know.value!string(); <BR>
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As bearophile said, you cannot change a value's type (which is a compile-time construct) with a runtime value, as is Known.type. <BR>
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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.<BR>
In your example, what happens if known.type != 1? <BR>
<BR>
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.<BR>
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