Question

我有一个类的函数成员，该成员应在执行时增加成员变量，但问题是它不能正常工作。因为输入值是随机创建的，所以我无法确切解释得到的值是什么

class Dice
{
public:
    virtual void rollDice() = 0;

};



class Player : public Dice
{
public:
    Player(){ };
    Player(int id, string name ,int score = 0) : pId(id), pName(name) , pScore(score) { };
    void rollDice();
    int desplayScore() { return pScore;}

private:
    int pId;
    std::string pName;
    int pScore;
    unsigned char playerDiceRolled;
};

void Player::rollDice()
{
    std::random_device rd;
    std::mt19937 eng(rd());
    std::uniform_int_distribution<> distr(1, 6);
    this->playerDiceRolled = distr(eng);
    std::cout << "player rolled:" << distr(eng) << "\n";
    this->pScore =+ distr(eng);
}
int main()
{

    Player A(1, "Player");

    A.rollDice();
    A.rollDice();
    std::cout << A.desplayScore();
    return 0;

}

根据随机值，结果会有所不同，但不是正确的结果。

Answer 1

this->playerDiceRolled = distr(eng);
std::cout << "player rolled:" << distr(eng) << "\n";
this->pScore =+ distr(eng);

每次您调用发行版时，都会生成一个新的不同的伪随机数。您调用了三次，所以得到了三个不同的值。

如果您只是复制cout行-或在调试器中单步执行程序-您会看到它的作用。

尝试这样的事情

this->playerDiceRolled = distr(eng);
std::cout << "player rolled:" << playerDiceRolled << "\n";
this->pScore += playerDiceRolled;

（包括Stephan注意到的+ =修复程序，我完全错过了）。

Answer 2

您有错字

this->pScore =+ distr(eng);

不增加pScore而是将其设置为该值。

您可能是想

this->pScore += distr(eng);

您应该重用随机生成的数字，而不要在rollDice的过程中生成不同的数字：

this->playerDiceRolled = distr(eng);
std::cout << "player rolled:" <<  this->playerDiceRolled << "\n";
this->pScore += this->playerDiceRolled;

Answer 3

您使用distr(eng)三次，将根据this产生三种不同的输出。

您的逻辑在这里也是错误的。 Player类不应是Dice所固有的，而应具有一个对象。我将代码更改为：（注意移动 roll Dice类的功能，并从 Player::rollDice 调用它）

class Dice
{
    public:
        unsigned char roll() {

            std::random_device rd;
            std::mt19937 eng(rd());
            std::uniform_int_distribution<> distr(1, 6);
            return distr(eng);
        }
};



class Player
{
    public:
        Player(){ };
        Player(int id, string name ,int score = 0) : pId(id), pName(name) , pScore(score) { 
        };
    void rollDice();
    int desplayScore() { return pScore;}

private:
    int pId;
    std::string pName;
    int pScore;
    unsigned char playerDiceRolled;
    Dice mDice;
};

void Player::rollDice()
{
    this->playerDiceRolled = mDice.roll();
    std::cout << "player rolled:" << playerDiceRolled << "\n";
    this->pScore += playerDiceRolled;
}
int main()
{

    Player A(1, "Player");

    A.rollDice();
    A.rollDice();
    std::cout << A.desplayScore();
    return 0;

}

Answer 4

谢谢大家我修复了它

#include <iostream>
#include <memory>
#include <vector>
#include <string>
#include <random>
using namespace std;



class Dice
{
public:
    virtual void rollDice() = 0;

};



class Player : public Dice
{
public:
    Player(){ };
    Player(int id, string name ,int score = 0) : pId(id), pName(name) , pScore(score) { };
    void rollDice();
    int desplayScore() { return pScore;}

private:
    int pId;
    std::string pName;
    int pScore;
    unsigned char playerDiceRolled;
};

void Player::rollDice()
{
    std::random_device rd;
    std::mt19937 eng(rd());
    std::uniform_int_distribution<> distr(1, 6);
    this->playerDiceRolled = distr(eng);
    std::cout << "player rolled:" << to_string(playerDiceRolled) << "\n";
    this->pScore += playerDiceRolled;
}
int main()
{

    Player A(1, "Player");

    A.rollDice();
    A.rollDice();
    std::cout << A.desplayScore();
    return 0;

}

成员函数执行时成员变量的增量

4 个答案: