Re: [boost] [any] boost::get style accessors

Subject: Re: [boost] [any] boost::get style accessors
From: Stefan (mstefanro_at_[hidden])
Date: 2010-04-28 13:27:03

Stefan wrote:
> Christoph Heindl wrote:
>> Hi all,
>>
>> I couldn't find any boost::get<T> style accessors for boost::any, so I
>> came up with an implementation that looks something along the
>> following lines.
>>
>> #include <boost/any.hpp>
>> #include <boost/call_traits.hpp>
>>
>> namespace boost {
>>
>>   template<class T>
>>   typename boost::call_traits<T>::reference get(any &a) {
>>     return boost::any_cast<typename boost::call_traits<T>::reference>(a);
>>   }
>>
>>   template<class T>
>>   typename boost::call_traits<T>::const_reference get(const any &a) {
>>     return boost::any_cast<typename 
>> boost::call_traits<T>::const_reference>(a);
>>   }
>> }
>>
>> In case it cannot be converted to the desired destination type a
>> bad_any_cast exception is thrown.
>>
>> The above code enables boost.any and boost.variant to be used
>> interchangeably as far as boost::get<T> is concerned.
>>
>> Any thoughts?
>>
>> Best regards,
>> Christoph
>> _______________________________________________
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>>
> You may want to extend this by adding support for get(any*) and get(any 
> const*). Also, for making them usable interchangeably via boost::get, 
> you need them to throw the same exception. Therefore, in case you are 
> using boost::any, you probably want to rethrow bad_any_cast to bad_get.
> 
> namespace boost {
>   template<class T>
>   typename boost::call_traits<T>::reference get(any &a) {
>         try {
>             return boost::any_cast<typename 
> boost::call_traits<T>::reference>(a);
>         } catch (boost::bad_any_cast const &) { throw(boost::bad_get()); }
>   }
> 
>   template<class T>
>   typename boost::call_traits<T>::const_reference get(const any &a) {
>         try {
>             return boost::any_cast<typename 
> boost::call_traits<T>::const_reference>(a);
>         } catch (boost::bad_any_cast const &) { throw(boost::bad_get()); }
>   }
>     
>     template <class T>
>     T* get (any *a) {
>         return boost::any_cast<T>(a);
>     }
>     
>     template <class T>
>     T const* get (const any *a) {
>         return boost::any_cast<T>(a);
>     }
> }
> 
> Yours,
>   Stefan
> 
> P.S. While looking through [1] I noticed that boost::bad_get is missing 
> a nothrow virtual dtor: virtual ~bad_get() throw() { }
> Unless I'm wrong, someone should probably add that there.
> 
> _______________________________________________
> Unsubscribe & other changes: 
> http://lists.boost.org/mailman/listinfo.cgi/boost
> 
Sorry, [1] = http://www.boost.org/doc/libs/1_42_0/boost/variant/get.hpp

Stefan