Question

我正在尝试使用VS-2013在c ++中实现一个纸牌游戏，我有一个“玩家”类。 “Player”类是抽象的，因为不会初始化该类的实际对象。相反，它只是继承到4个不同的玩家类（有4种不同的游戏策略） - “PlayerType1”到“PlayerType4”。

这是我的Player.h文件：

#ifndef PLAYER_H_
#define PLAYER_H_

#include <iostream>
#include "Hand.h"
using namespace std;

class Player : public Hand {
private:
    const string name;
protected:
    Hand myHand;
public:
    string getName();   //Returns the name of the player
    virtual int getShapeToAsk() = 0;
    virtual int getPlayerToAsk() = 0;
    virtual ~Player();
};

class PlayerType1 : public Player {  //For strategy 1
    PlayerType1();
    virtual int getShapeToAsk() override;
    virtual int getPlayerToAsk() override;
    ~PlayerType1();
};

class PlayerType2 : public Player {  //For strategy 2
    PlayerType2();
    virtual int getShapeToAsk() override;
    virtual int getPlayerToAsk() override;
    ~PlayerType2();
};

class PlayerType3 : public Player {  //For strategy 3
private:
    int myNumber, numOfPlayers, nextPlayer;
public:
    PlayerType3(int myNumber, int numOfPlayers);
    virtual int getShapeToAsk() override;
    virtual int getPlayerToAsk() override;
    ~PlayerType3();
};

class PlayerType4 : public Player {  //For strategy 4
private:
    int myNumber, numOfPlayers, nextPlayer;
public:
    PlayerType4(int myNumber, int numOfPlayers);
    virtual int getShapeToAsk() override;
    virtual int getPlayerToAsk() override;
    ~PlayerType4();
};

#endif

这是我的Player.cpp文件：

#include <iostream>
#include <vector>
#include "Hand.h"
#include "Player.h"
using namespace std;

//Player functions

string Player::getName(){
    return (this->name + " " + this->toString());
}

Player::~Player(){}

//PlayerType1 functions

PlayerType1::PlayerType1(){}

int PlayerType1::getShapeToAsk(){
    int maxCount = 0, maxValue, currValue, count;
    for (std::vector<Card*>::reverse_iterator i = this->myHand.getCards().rbegin(); i != this->myHand.getCards().rend(); i++){
        count = 1;
        currValue = (**i).getValue();
        for (i; (i != this->myHand.getCards().rend()) && ((**i).getValue() == currValue); ++i){
            count++;
        }
        if (count > maxCount){
            maxCount = count;
            maxValue = currValue;
            if (maxCount == 4) // no need to look at the rest of the hand
                break;
        }
    }
    return maxValue;
}

int PlayerType1::getPlayerToAsk(){ return -1; } //-1 means "I am a player of type 1 or 2". Game's responsibility to change later.

PlayerType1::~PlayerType1(){}

//PlayerType2 functions

PlayerType2::PlayerType2(){}

int PlayerType2::getShapeToAsk(){
    int minCount = 5, minValue, currValue, count;
    for (std::vector<Card*>::iterator i = this->myHand.getCards().begin(); i != this->myHand.getCards().end(); i++){
        count = 1;
        currValue = (**i).getValue();
        for (i; (i != this->myHand.getCards().end()) && ((**i).getValue() == currValue); ++i){
            count++;
        }
        if (count < minCount){
            minCount = count;
            minValue = currValue;
            if (minCount == 1) // no need to look at the rest of the hand
                break;
        }
    }
    return minValue;
}

int PlayerType2::getPlayerToAsk(){ return -1; } //-1 means "I am a player of type 1 or 2". Game's responsibility to change later.

PlayerType2::~PlayerType2(){}

//PlayerType3 functions

PlayerType3::PlayerType3(int myNumber, int numOfPlayers){
    this->myNumber = myNumber;
    this->numOfPlayers = numOfPlayers;
    if (myNumber == 1) this->nextPlayer = 2;
    else this->nextPlayer = 1;
}

int PlayerType3::getShapeToAsk(){
    int maxCount = 0, maxValue, currValue, count;
    for (std::vector<Card*>::reverse_iterator i = this->myHand.getCards().rbegin(); i != this->myHand.getCards().rend(); i++){
        count = 1;
        currValue = (**i).getValue();
        for (i; (i != this->myHand.getCards().rend()) && ((**i).getValue() == currValue); ++i){
            count++;
        }
        if (count > maxCount){
            maxCount = count;
            maxValue = currValue;
            if (maxCount == 4) // no need to look at the rest of the hand
                break;
        }
    }
    return maxValue;
}

int PlayerType3::getPlayerToAsk(){
    int temp = this->nextPlayer;
    this->nextPlayer++;
    while ((this->nextPlayer == this->myNumber) || (this->nextPlayer > this->numOfPlayers)){
        if (this->nextPlayer == this->myNumber) this->nextPlayer++;
        if (this->nextPlayer > this->numOfPlayers) this->nextPlayer = 1;
    }
    return temp;
}

PlayerType3::~PlayerType3(){}

//PlayerType4 functions

PlayerType4::PlayerType4(int myNumber, int numOfPlayers){
    this->myNumber = myNumber;
    this->numOfPlayers = numOfPlayers;
    if (myNumber == 1) this->nextPlayer = 2;
    else this->nextPlayer = 1;
}

int PlayerType4::getShapeToAsk(){
    int minCount = 5, minValue, currValue, count;
    for (std::vector<Card*>::iterator i = this->myHand.getCards().begin(); i != this->myHand.getCards().end(); i++){
        count = 1;
        currValue = (**i).getValue();
        for (i; (i != this->myHand.getCards().end()) && ((**i).getValue() == currValue); ++i){
            count++;
        }
        if (count < minCount){
            minCount = count;
            minValue = currValue;
            if (minCount == 1) // no need to look at the rest of the hand
                break;
        }
    }
    return minValue;
}

int PlayerType4::getPlayerToAsk(){
    int temp = this->nextPlayer;
    this->nextPlayer++;
    while ((this->nextPlayer == this->myNumber) || (this->nextPlayer > this->numOfPlayers)){
        if (this->nextPlayer == this->myNumber) this->nextPlayer++;
        if (this->nextPlayer > this->numOfPlayers) this->nextPlayer = 1;
    }
    return temp;
}

PlayerType4::~PlayerType4(){}

我收到以下错误：

Error       error C2512: 'Player' : no appropriate default constructor available    <PATH>\player.cpp

该类型总共有4个错误，每个错误都指向PlayerType1到PlayerType4的构造函数。

当我向我的“Player”类添加一个空的默认构造函数时，它解决了问题，我得到了一个成功的构建。但是，我不明白为什么我需要为“Player”类定义默认构造函数，因为我从不初始化该类的对象。

我还应该提到我的项目中有另一个类（“Card”类）是抽象的，只是由其他类继承（“FigureCard”和“NumericCard”），并且没有构造函数，派生类有自己的构造函数，这不会导致错误。我没有看到差异。

我搜索了其他问题，但它们都与未定义默认构造函数的情况有关，并且在代码中的其他位置尝试初始化该类。这不是我的情况，因为我没有初始化类“Player”的对象，只有4个派生类。

请帮忙！提前谢谢。

Answer 1

即使您的Player类是抽象的，您也必须定义构造函数，因为您的类具有成员。当您创建派生类（任何PlayerType）类的实例时，它将调用基类的构造函数。这就是继承的作用......

在这种情况下，让它受到保护（无论如何，公开它都是无用的，因为它是一个纯粹的虚拟类）。

Answer 2

您的Player班级有private: const string name;个成员。看看你的Card班级;我打赌它没有这样的成员。这就是区别。

问题是，const string name;成员必须以某种方式初始化，因为它是private，它必须在Player类中初始化。（语言规则禁止从派生类初始化类的私有成员。）因此，Player类必须具有将初始化name成员的构造函数。空构造函数实现了这一点。

c ++错误错误C2512没有适当的默认构造函数可用

2 个答案: