[Boost-users] [MultiIndex] Key extraction from a base member

Hi. I have the following problem with MultiIndex. For struct Base { int id; }; struct Der : Base { }; I can't make a key extractor. This way typedef multi_index_container< Der, indexed_by< ordered_unique >

Set;

doesn't work because &Der::id is of type pointer to member of Base. This other typedef multi_index_container< Der, indexed_by< ordered_unique >

Set;

doesn't work because of the ChainedPtr overloads in member. I tried casting &Der::id to the appropiate type, but couldn't make it work. Maybe the solution is to put some enable_ifs in member. Regards, Bruno