Question

Pointer to members are not used very much but they are really powerful, how have you used them and what’s the coolest things you’ve done?

Edit: This is not so much to list things that are possible, for example listing boost::bind and boost::function aren’t good. Instead maybe a cool usage with them? I know they’re very cool in themselves but that’s not what this is about.

Answer 1

I once was needed to operate with criteria data as pure structure to be able to store the list of all criteria in the queue. And I had to bind the structure with the GUI and other filter elements, etc. So I came up with the solution where pointers to members are used as well as pointers to member functions.

Let’s say you have an

struct Criteria {     typedef std::string Criteria::* DataRefType;     std::string firstname;     std::string lastname;     std::string website; }; 

Than you can wrap criteria field and bind with the string representation of the field with

class Field { public:     Field( const std::string& name,            Criteria::DataRefType ref ):         name_( name ),         ref_( ref )     {}     std::string getData( const Criteria& criteria )     {         return criteria.*ref_;     }     std::string name_; private:     Criteria::DataRefType ref_; }; 

Then you can register all the fields to use whenever you want: GUI, serialization, comparison by field names, etc.

class Fields { public:     Fields()     {         fields_.push_back( Field( 'First Name', &Criteria::firstname ) );         fields_.push_back( Field( 'Last Name', &Criteria::lastname ) );         fields_.push_back( Field( 'Website', &Criteria::website ) );     }     template < typename TFunction >     void forEach( TFunction function )     {         std::for_each( fields_.begin(), fields_.end(),                        function );     } private:     std::vector< Field > fields_; }; 

By calling for instance fields.forEach( serialization ); or

GuiWindow( Criteria& criteria ):     criteria_( criteria ) {     fields_.forEach( std::bind1st(                           std::mem_fun( &GuiWindow::bindWithGui ),                          this ) ); } void bindWithGui( Field field ) {     std::cout << 'name ' << field.name_               << ' value ' << field.getData( criteria_ ) << std::endl; };