c++ - 如何删除包含结构的 map 或包含结构的 map ？

Question

我有下面的代码来创建一个 map ，其中包含一个包含结构图的结构。我的问题是如何在不留下任何内存泄漏的情况下从 providerMap 中删除一个元素。我可以只做一个 providerMap[prov_id].erase() 还是我需要在第二个或更复杂的时候做一个删除？

struct uriPrivs {
    std::string name;
    uchar properties;
};
struct providerValues {
    int KeepAlive;
    std::map<std::string /*uri*/, uriPrivs> uris;
};
std::map<std::string /*prov_id*/, providerValues> providerMap;

RISStorageManager::risStorageResponse RISStorageManager::update_provider(const std::string &prov_id, int KeepAlive) {

    if (providerMap.find(prov_id) == providerMap.end()) {
        providerValues x;
        x.KeepAlive = KeepAlive;
        providerMap[prov_id] = x;
        return risStorageCreated;
    } else {
        providerMap[prov_id].KeepAlive = KeepAlive;
        return risStorageUpdated;
    }
}
RISStorageManager::risStorageResponse RISStorageManager::update_uri(const std::string &prov_id, std::map<std::string, uriPrivs> &uris) {
    providerMap[prov_id].uris = uris;
}

Answer 1

如前所述，您无需在此处显式释放任何内存。您自己并不是在“新建”任何东西。一切都将由 map 对象的析构函数处理。

您可以稍微压缩 update_provider 函数...

RISStorageManager::risStorageResponse update_provider(const std::string &prov_id, int KeepAlive)
{
   RISStorageManager::risStorageResponse response = (providerMap.end() == providerMap.find(prov_id)) ?
      risStorageCreated : risStorageUpdated;

   providerMap[prov_id].KeepAlive = KeepAlive;

   return response;
}

这里有一些测试代码来解释一些事情......

int main(int argc, char *argv [])
{
   // Create new provider and print result...
   std::cout << update_provider("test1", 1) << std::endl;

   // Add a URI to the first provider for fun...
   providerMap["test1"].uris["www.google.com"].name = "GOOGLE";
   providerMap["test1"].uris["www.google.com"].properties = 0xFF;

   // Create new provider and print result...
   std::cout << update_provider("test2", 1) << std::endl;

   // Create new provider and print result...
   std::cout << update_provider("test3", 1) << std::endl;

   // Update first provider and print result...
   std::cout << update_provider("test1", 0) << std::endl;

   // Explicitly remove first provider if you want...
   providerMap.erase("test1");

   //
   // Now only 2 providers are in map (test2 and test3).
   // The program will exit and the STL map destructors will take care of any
   // memory deallocation that is needed to clean up the maps. You don't need
   // to explicitly clean up anything unless you want to remove providers from
   // your map explicitly.
   //

   return 0;
}