我試圖根據這個答案解決昨天在 SO 上提出的問題。
我已經修改了此處給出的代碼以使用std::any而不是void*. 我目前擁有的代碼如下：
#include <iostream>
#include <map>
#include <vector>
#include <any>
#include <typeindex>
struct cStreet{};
struct cHouse{};
struct cComputer{};
struct cBook{};
class cPlayer
{
public:
struct Properties
{
std::vector<cStreet*> Streets;
std::vector<cHouse*> Houses;
std::vector<cComputer*> Computers;
std::vector<cBook*> Book;
};
cPlayer(std::string name) : m_name{name}{};
~cPlayer(){};
std::string m_name{};
Properties m_Properties;
std::map<std::type_index, std::any> myMap{{typeid(cStreet*), m_Properties.Streets}, {typeid(cHouse*), m_Properties.Houses}, {typeid(cComputer*), m_Properties.Computers}, {typeid(cBook*), m_Properties.Book}};
template<typename T> void buy(T& Arg);
};
template<typename T> void cPlayer::buy(T& Arg)
{
std::cout << m_name.c_str() << " : Do you want buy this ?" <<typeid(Arg).name() << std::endl;
//Todo: Decision (here yes)
std::any_cast<std::vector<decltype(&Arg)>>(myMap.at(typeid(&Arg))).push_back(&Arg); //THIS DOESN'T ADD ELEMENTS INTO THE VECTORS BECAUSE STD::ANY HAS A COPY OF THE ORIGINAL VECTORS
}
int main()
{
//create objects
cStreet S;
cHouse H;
cComputer C;
cBook B;
cPlayer c("anoop");
//lets test our code
c.buy(S);
c.buy(H);
c.buy(C);
c.buy(B);
}
該問題是，當我寫的
std::any_cast<std::vector<decltype(&Arg)>>(myMap.at(typeid(&Arg))).push_back(&Arg);
這不會將( push_back) 元素添加到原始向量中，而是添加它的副本。
如何添加元素到原來的載體m_Properties.Streets，m_Properties.Houses等等？我嘗試使用std::ref但我無法成功使用std::ref.
uj5u.com熱心網友回復：
基于此答案，將您重新定義myMap為：
std::map<std::type_index, std::any> myMap{
{typeid(cStreet*), std::ref(m_Properties.Streets)},
{typeid(cHouse*), std::ref(m_Properties.Houses)},
{typeid(cComputer*), std::ref(m_Properties.Computers)},
{typeid(cBook*), std::ref(m_Properties.Book)}
};
然后根據訪問原文強制any轉換為對應的reference_wrapper型別：Tvector
template<typename T>
void cPlayer::buy(T& Arg) {
// ...
using mapped_type = std::reference_wrapper<std::vector<T*>>;
std::any_cast<mapped_type>(myMap.at(typeid(T*))).get().push_back(&Arg);
// ...
}
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