[Boost-users] boost multi-index container find method.

17 Sep 2009

      Hello Joaquin,

I have a class like below that uses mult-index container's find
method.  I have a record pattern as below initially:

Idx : 100 Flag : 5
Idx : 200 Flag : 5
Idx : 300 Flag : 5
Idx : 400 Flag : 5

I modify the flag for index 100 to 6 & take a dump, the change is OK

Idx : 100 Flag : 6
Idx : 200 Flag : 5
Idx : 300 Flag : 5
Idx : 400 Flag : 5

I modify the flag for 100 back to 5 and take a dump, which is also fine.

Idx : 100 Flag : 5
Idx : 200 Flag : 5
Idx : 300 Flag : 5
Idx : 400 Flag : 5

Now I do a find based on flag value set to 5 I get the results as below:

Idx : 200 flag : 5

While find functionally is correct in picking up the correct data, but
I am wondering why it doesnt pick the first record (100) which has the
flag value set to 5? am I missing something in the indexing definition
in the container itself?

Thanks
/R

=========================

using namespace std;

#include <boost/lambda/lambda.hpp>
#include <boost/multi_index_container.hpp>
#include <boost/multi_index/ordered_index.hpp>
#include <boost/multi_index/member.hpp>
#include <iostream>
#include <iterator>
#include <iostream>
#include <string>

struct Token {

unsigned long  mIdx;
unsigned char mflag;

public:
       Token(unsigned long pIdx, unsigned char pflag):
                           mIdx(pIdx), mflag(pflag){}

       void Update(unsigned char pflag) {
            mflag = pflag;
       }

       ~Token() {
           mIdx =  0;
           mflag = 1;
       }
};

struct mIdx{};
struct mflag{};

using namespace boost::multi_index;
namespace ll = boost::lambda;

typedef multi_index_container<
 Token,
   indexed_by<
       ordered_unique<
           tag <mIdx>, BOOST_MULTI_INDEX_MEMBER(Token,unsigned long,mIdx)>,
       ordered_non_unique<
           tag <mflag>, BOOST_MULTI_INDEX_MEMBER(Token,unsigned char,mflag)>
   >
...
tToken;
class TokenMaster {
   tToken TokenContainer;
public:

 unsigned long getByFlag(unsigned long useFlag);
 bool modify(unsigned long idx, unsigned char flag);
 bool insert(unsigned long, unsigned char);
 void dump();

};

unsigned long TokenMaster::getByFlag(unsigned long useFlag) {

   typedef tToken::index<mflag>::type itflag;

   itflag& mflag_index = TokenContainer.get<mflag>();
   tToken::index_iterator<mflag>::type flagit = mflag_index.find(useFlag);
   if (flagit == mflag_index.end()) {
       return 0;
   }
   printf("Idx : %d flag : %d\n", flagit->mIdx, flagit->mflag);
   return flagit->mIdx;
}

bool TokenMaster::modify(unsigned long idx, unsigned char flag) {

   tToken::iterator itIp=TokenContainer.find(idx);

   if (itIp == TokenContainer.end())
       return false;

   return TokenContainer.modify(itIp,(&ll::_1)->*&Token::mflag=flag);
}

bool TokenMaster::insert(unsigned long idx, unsigned char flag) {
   tToken::iterator it;
   bool secres;

   std::pair<tToken::iterator, bool> result =
                   TokenContainer.insert(Token(idx, flag));
   it = result.first;
   secres = result.second;
   if (secres)
       return true;
   else
       return false;
}

void TokenMaster::dump()
{
   unsigned long count = 0;
   printf("\n\n List of indexes\n");
   for (tToken::iterator it = TokenContainer.begin(),
       it_end=TokenContainer.end(); it != it_end; ++it, count++)
   {
       printf("Idx : %d Flag : %d\n", it->mIdx, it->mflag);
   }
   printf("\n");
}

main() {
 TokenMaster T1;
 T1.insert(100, 5);
 T1.insert(200, 5);
 T1.insert(300, 5);
 T1.insert(400, 5);
 T1.dump();
 printf("Modifiying 100 to 6\n");
 T1.modify(100, 6);
 T1.dump();
 printf("Modifiying 100 back to 5\n");
 T1.modify(100, 5);
 T1.dump();

 printf("\n\nGet by flag \n");
 T1.getByFlag(5);
}

==========================

[Boost-users] boost multi-index container find method.

Ramesh