Duane Murphy writes:
How do I iterate over a type list and call a function? MPL?
I have a base class BASE that has several subclasses A, B, C that have special capabilities, but no way to identify those capabilities aside from the type.
I would like to determine if an object of type BASE is also of one of the special subclasses:
ie void f( BASE* base) { if ( dynamic_cast< A* >( base ) != NULL ) { some_function( dynamic_cast< A* >( base ) ); } else if ( dynamic_cast< B* >( base ) != NULL ) { some_function( dynamic_cast< B* >( base ) ); } else if ( dynamic_cast< C* >( base ) != NULL ) { some_function( dynamic_cast< C* >( base ) ); } }
I think you can see why I'd like a type list iterator solution to this.
Try this:
struct do_something
{
do_something( BASE* base ) : m_base( base ) {}
template< typename T > void operator()( mpl::identity<T> ) const
{
if ( T* x = dynamic_cast< T* >( this->m_base ) )
some_function( x );
}
BASE* m_base;
};
mpl::for_each<
mpl::vector
I have arranged for the some_function to be a template as well to make things easier.
What I am looking for is the equivalent of find_if() but for types and done at run time. I looked over MPL, but MPL seems to apply at compile time without a door to the run time world. :-)
Not true :), but 'for_each' is indeed not documented at the moment. -- Aleksey Gurtovoy MetaCommunications Engineering