爲「mapped_type」的std ::地圖初始化不匹配構造錯誤

我把這種現象稱之爲一類「卡」，我試圖來存儲一些在一個std ::對象地圖 Card.hpp：爲「mapped_type」的std ::地圖初始化不匹配構造錯誤

class Card 
{ 
public: 
    enum ValueType { NOVALUE, ACE }; 
    enum FaceType { NOFACE, CLUBS }; 

    Card(const ValueType & _value, const FaceType & _face); 
    Card(const Card & _card); 
private: 
    ValueType m_value; 
    FaceType m_face; 
};

這是我如何存儲和訪問它： Deck.hpp：

#include <map> 

class Card; 

class Deck 
{ 
    public: 
     Deck(); 

     std::size_t length() const; 

     Card get_card(const int & _num); 

    private: 
     std::map<int, Card> m_deck; 
};

Deck.cpp：

#include "Card.hpp" 

Deck::Deck() 
{ 
    m_deck.insert(std::pair<int, Card>(0, Card(Card::NOVALUE, Card::NOFACE))); 
    m_deck.insert(std::pair<int, Card>(1, Card(Card::ACE, Card::CLUBS))); 
} 
std::size_t Deck::length() const 
{ 
    return m_deck.size(); 
} 

Card Deck::get_card(const int & _num) 
{ 
    return m_deck[_num]; 
}

現在，當我編譯它，我得到以下錯誤：

/usr/include/c++/4.6/bits/stl_map.h:453:45: error: no matching constructor for initialization of 'mapped_type' (aka 'Card') 
      __i = insert(__i, value_type(__k, mapped_type())); 
              ^
Deck.cpp:69:18: note: in instantiation of member function 'std::map<int, Card, std::less<int>, std::allocator<std::pair<const int, Card> > >::operator[]' requested here 
    return m_deck[_num]; 
       ^
./Card.hpp:30:2: note: candidate constructor not viable: requires 2 arguments, but 0 were provided 
     Card(const ValueType & _value, const FaceType & _face); 
     ^
./Card.hpp:32:2: note: candidate constructor not viable: requires 1 argument, but 0 were provided 
     Card(const Card & _card); 
     ^
1 error generated.

爲什麼會出現這個錯誤？我僅將卡用作價值！

來源

2012-11-26 Anupam Srivastava