我有以下unordered_map,它使用类型为int的键将指针映射到Item类型的对象。
typedef std::unordered_map<int, Item*> ItemList;
ItemList Items;
但是,在我的addItem方法中,我在编译时收到一个奇怪的错误。
void ItemManager::addItem(Item *it) {
int i = it->getItemID();
Items.insert(ItemList::value_type(i, *it));
}
收率:
item_manager.cc: In member function ‘void ItemManager::addItem(Item*)’:
item_manager.cc:31:51: error: no matching function for call to ‘std::pair<const int, Item*>::pair(int&, Item&)’
item_manager.cc:31:51: note: candidates are:
/usr/include/c++/4.6/bits/stl_pair.h:140:2: note: template<class ... _Args1, class ... _Args2> std::pair::pair(std::piecewise_construct_t, std::tuple<_Args1 ...>, std::tuple<_Args2 ...>)
/usr/include/c++/4.6/bits/stl_pair.h:135:2: note: template<class _U1, class _U2> std::pair::pair(std::pair<_U1, _U2>&&)
/usr/include/c++/4.6/bits/stl_pair.h:131:2: note: template<class _U1, class _U2, class> std::pair::pair(_U1&&, _U2&&)
/usr/include/c++/4.6/bits/stl_pair.h:125:2: note: template<class _U2, class> std::pair::pair(const _T1&, _U2&&)
/usr/include/c++/4.6/bits/stl_pair.h:120:2: note: template<class _U1, class> std::pair::pair(_U1&&, const _T2&)
/usr/include/c++/4.6/bits/stl_pair.h:112:17: note: constexpr std::pair<_T1, _T2>::pair(const std::pair<_T1, _T2>&) [with _T1 = const int, _T2 = Process*, std::pair<_T1, _T2> = std::pair<const int, Process*>]
/usr/include/c++/4.6/bits/stl_pair.h:112:17: note: candidate expects 1 argument, 2 provided
/usr/include/c++/4.6/bits/stl_pair.h:108:21: note: template<class _U1, class _U2> constexpr std::pair::pair(const std::pair<_U1, _U2>&)
/usr/include/c++/4.6/bits/stl_pair.h:103:26: note: constexpr std::pair<_T1, _T2>::pair(const _T1&, const _T2&) [with _T1 = const int, _T2 = Process*]
/usr/include/c++/4.6/bits/stl_pair.h:103:26: note: no known conversion for argument 2 from ‘Process’ to ‘Process* const&’
/usr/include/c++/4.6/bits/stl_pair.h:99:26: note: constexpr std::pair<_T1, _T2>::pair() [with _T1 = const int, _T2 = Process*]
/usr/include/c++/4.6/bits/stl_pair.h:99:26: note: candidate expects 0 arguments, 2 provided
任何可能导致这些错误的想法?我是C ++的新手,所以我一直在研究我在网络上找到的无序映射的例子。任何帮助是极大的赞赏。拜托,谢谢!
答案 0 :(得分:4)
地图中的值属于Item*
,因此您需要插入Item*
,而不是Item
。这一行
Items.insert(ItemList::value_type(i, *it));
应该是
Items.insert(ItemList::value_type(i, it));
答案 1 :(得分:2)
您无需取消引用指针:
void ItemManager::addItem(Item *it) {
int i = it->getItemID();
Items.insert(ItemList::value_type(i, it));
}