Re: [pclasses-devel] Unification of Any and Variant

[Christian P. <cp...@se...>]

Am Donnerstag 20 Januar 2005 04:41 schrieb Marc Duerner:
> I just had the idea that one could unify P::Util::Any and P::Util::Variant.
> They do basically both the same, but Any uses typeid and casting, while
> Variant (the class formerly known as LexT) uses stream based conversion.

I also had this idea.

> This would simply require to add a convertTo member function to Any that
> allows stream based conversion additionally to the any_casts:
>
> template <typename ValueType>
> ValueType convertTo(const ValueType& defVal = ValueType()) const {
>   Any::holder<ValueType>* valHolder = 0;
>   valHolder = dynamic_cast< Any::holder<ValueType>* >(m_data);
>   if(valHolder) {
>     return valHolder->value();
>   }
>
>   ValueType retVal(defVal);
>   std::stringstream ss;
>   m_data->output(ss);
>   ss >> retVal;
>   return retVal;
> }
>
>
> The dynamic_cast is a short cut.
>
> In code you would do this:
>
> Any myAny(5);
> string s = myAny.convertTo<std::string>();

this rocks!

> or we add a type conversion member to Any that does this automatically:
>
> template <typename T>
> operator T() const throw() {
>  return this->template convertTo<T>();
> }
>
>
> Does anybody see a problem with this?

No - please merge them. Maybe we should also move Any to the P namespace.

> Marc

Greetings,
Christian