[Boost-users] Boost:multi-index Question on usage of project & modify_key

Subject: [Boost-users] Boost:multi-index Question on usage of project & modify_key
From: Ramesh (rramesh1_at_[hidden])
Date: 2009-01-14 19:55:40

Hello.

I am using projection technique & modify_key in one of my member functions:

Assuming I have the following data in the container:

ObjId      ObjIp               ObjIndex               pMyObj
-------------------------------------------------------------------------------------
ID1        10.10.1.2    	     1     		0x10239032
ID2        10.10.1.3  	     2     		0x23423423
ID3        10.10.1.4               3		0x23132423

The member function 'UpdateKeyObjId' accepts the value on column 3 as
key & changes the corresponding value
for the field in Column 1.

My code seems to work fine for all rows except the last row. When I
use modify key on the last record, the app crashes at
the highlighted line.  I am not sure if my usage of project &
modify_key right, could someone please point out if there
are any errors in the usage?

Thanks
/R

struct MyMap
{
        std::string		ObjId;	
        unsigned long		ObjIp;	
        unsigned long		ObjIndex;	
          MyObj			*pMyObj;	

        MyMap(std::string param_ObjId, unsigned long param_ObjIp,
                                                unsigned long param_ObjIndex, MyObj*  param_pMyObj):
                                        ObjId(param_ObjId), ObjIp(param_ObjIp),
                                                ObjIndex(param_ObjIndex), pMyObj(param_pMyObj) {}
        ~MyMap(){

                ObjId.erase();
                ObjIp       = 0;
                ObjIndex    = 0;
                pMyObj     = 0;

        }

};

struct ObjId{};
struct ObjIp{};
struct ObjIndex{};

typedef multi_index_container<
  MyMap,
        indexed_by<
                ordered_unique<
                        tag <ObjId>, BOOST_MULTI_INDEX_MEMBER(MyMap,std::string,ObjId)>,
                ordered_non_unique<
                              tag<ObjIp>,BOOST_MULTI_INDEX_MEMBER(MyMap,unsigned long,ObjIp)>,
            ordered_unique<
                              tag<ObjIndex>,BOOST_MULTI_INDEX_MEMBER(MyMap,unsigned long,ObjIndex)>
	>
> tMyObjMap;

class MyObjContainer{

        private:
                tMyObjMap MyContainer;
        public:
                UpdateKeyObjId(unsigned long, std::string);
};

bool MyObjContainer::UpdateKeyObjId(unsigned long param_ObjIndex,
std::string param_ObjId) {

    typedef tMyObjMap::index<ObjIndex>::type tMyObjMapByIndex;
    tMyObjMapByIndex& ObjIndex_index = MyContainer.get<ObjIndex>();

    tMyObjMap::index_iterator<ObjIndex>::type it =
ObjIndex_index.find(param_ObjIndex);

    typedef tMyObjMap::index<ObjId>::type tMyObjMapById;
    tMyObjMapById::iterator ObjIdit = MyContainer.project<0>(it);

    // Use the modify_key method to update the ObjIp key with new value
    return MyContainer.get<0>().modify_key(ObjIdit, ll::_1 = param_ObjId);
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

}