Re: [boost] Properties and boost::any / boost::program_options

From: Vladimir Prus (ghost_at_[hidden])
Date: 2004-12-27 07:38:33

On Sunday 26 December 2004 16:35, Dirk Gregorius wrote:

> I have a text file which defines several properties. For example:
>
> // Properties.txt
> "Position" "1.0 2.0 3.0"
> "Color" "1.0 0.0 0.0"
> "Intensity" "500"
.....
>        properties.push_back( Property( key, value ) );
.....
>        Vector3 position = any_cast<Vector3>( pos->Value );

> 1. Is it possible to use boost::any in this way? If yes - where and how
> do I have to implement the conversions?

To the best of my knowledge -- no. boost::any does not support lexical casting 
of content that you seem to want. You can use

    lexical_cast<Vector3>*any_cast<string>(&pos->Value)

or something like that.

> 2. If this is not possible could I use boost::programm_options instead
> for the value type? How and where do I have to implement the conversion
> here.

You'd overload the 'validate' function for your Vector3, I think. The idea is 
that you'll have to specify the types of all properties when declaring the 
options.

> 3. Would you suggest to define a simple Value class like this when I can
> not use any boost classes:
>
> class Value
> {
> public:
>     Value();
>     Value( const std::string& )
>
>     template<typename T>
>     T As(void ) const;
>
> private:
>     std::string m_Value;
> }

Seems like lexical_cast does what you want.

- Volodya