对远期申报感到困惑

#pragma once
#include "Player.h"
class Player;
//class SmallHealth;
const int kNumOfCards = 3; //for Player class also
const int kCardLimit = 3;
class Cards
{
private:
protected:
    int turnsInEffect;
    Player *owner;
public:
    Cards()
    {turnsInEffect = 1;}
    void AssignOwner(Player &player)
    {
        owner = &player;
    }
    virtual void PlayCard()
    {}
    virtual ~Cards(void)
    {}
};
class SmallHealth : public Cards
{
public:
    void PlayCard()
    {
        turnsInEffect = 1;
        owner->SetHealth(owner->GetHealth() + 5);
        //check if health goes over
        if(owner->GetHealth() > owner->GetHealthLimit())
        {
            owner->SetHealth(owner->GetHealthLimit());
        }
        turnsInEffect--;
    }
};

我认为通过声明类Player我不会得到这些错误:

error C2027: use of undefined type 'Player

参见'Player'的声明

error C2227: left of '->SetHealth' must point to ...

检查错误2027，似乎我必须在Cards类之前显式地拥有整个类，但我认为前向类声明将使其不必要。我如何设置它是由Player类创建和分配Cards类的子类并存储在Player类中。继承Cards类的子类将调用Player类的函数。我有一个艰难的时间来确保两个类识别彼此的类