在 std::map 中使用 char* 作为键 [英] Using char* as a key in std::map

问题描述

我想弄清楚为什么下面的代码不起作用，我假设这是使用 char* 作为键类型的问题，但是我不确定如何解决它或它为什么会发生.我使用的所有其他函数(在 HL2 SDK 中)都使用 char*，因此使用 std::string 会导致很多不必要的并发症.

I am trying to figure out why the following code is not working, and I am assuming it is an issue with using char* as the key type, however I am not sure how I can resolve it or why it is occuring. All of the other functions I use (in the HL2 SDK) use char* so using std::string is going to cause a lot of unnecessary complications.

std::map<char*, int> g_PlayerNames;

int PlayerManager::CreateFakePlayer()
{
    FakePlayer *player = new FakePlayer();
    int index = g_FakePlayers.AddToTail(player);

    bool foundName = false;

    // Iterate through Player Names and find an Unused one
    for(std::map<char*,int>::iterator it = g_PlayerNames.begin(); it != g_PlayerNames.end(); ++it)
    {
        if(it->second == NAME_AVAILABLE)
        {
            // We found an Available Name. Mark as Unavailable and move it to the end of the list
            foundName = true;
            g_FakePlayers.Element(index)->name = it->first;

            g_PlayerNames.insert(std::pair<char*, int>(it->first, NAME_UNAVAILABLE));
            g_PlayerNames.erase(it); // Remove name since we added it to the end of the list

            break;
        }
    }

    // If we can't find a usable name, just user 'player'
    if(!foundName)
    {
        g_FakePlayers.Element(index)->name = "player";
    }

    g_FakePlayers.Element(index)->connectTime = time(NULL);
    g_FakePlayers.Element(index)->score = 0;

    return index;
}

推荐答案

您需要为映射提供一个比较函子，否则它比较的是指针，而不是它指向的以空字符结尾的字符串.一般来说，只要您希望地图键成为指针，就会出现这种情况.

You need to give a comparison functor to the map otherwise it's comparing the pointer, not the null-terminated string it points to. In general, this is the case anytime you want your map key to be a pointer.

例如:

struct cmp_str
{
   bool operator()(char const *a, char const *b) const
   {
      return std::strcmp(a, b) < 0;
   }
};

map<char *, int, cmp_str> BlahBlah;

这篇关于在 std::map 中使用 char* 作为键的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！