Re: std::multimap with composite key?

From:

"Daniel T." <daniel_t@earthlink.net>

Newsgroups:

comp.lang.c++

Date:

Thu, 22 Jan 2009 14:58:55 -0800 (PST)

Message-ID:

<8cad4540-7f18-4596-8303-03f979b21954@35g2000pry.googlegroups.com>

On Jan 22, 10:41 am, PeteOlcott <PeteOlc...@gmail.com> wrote:

On Jan 19, 2:28 pm, "Daniel T." <danie...@earthlink.net> wrote:

In addition to the other advice given. Note that if you use a map, the
name + value in the key won't be connected to the name + value in the
struct except by coincidence.

// Here is my solution:

#include <stdio.h>
#include <map>
#include <string>

struct NameValuePair
{
  std::string Name;
  std::string Value;

};

int main()
{
  NameValuePair nvp;
  std::multimap<std::string, NameValuePair> nvp_multimap;

  nvp.Name = "Name"; nvp.Value = "Pete";
  nvp_multimap.insert(std::make_pair(nvp.Name + nvp.Value, nvp));

  nvp.Name = "Name"; nvp.Value = "Pete";
  nvp_multimap.insert(std::make_pair(nvp.Name + nvp.Value, nvp));

  printf("nvp_map.size(%d)\n", nvp_multimap.size());

  std::multimap<std::string, NameValuePair>::iterator result;
  result = nvp_multimap.find("NamePete");

  if (result != nvp_multimap.end())

    {
      // the problem with this solution is: what if
      // someone does this?
      result->Name = "Joe";

      // the key for the object will stll be "NamePete"
      // but the value will be "JoePete"

      // you should probably use a set/multiset instead.

printf("Found It!\n");

}

else
printf("Not Found!\n");

}