c++ - 使用 push_back 在类中填充结构的值

Question

您好，我正在做一个编程 II 项目。对于我在这里犯的任何错误，我提前道歉(这是我的第一篇文章)。我正在开发一个程序来模仿游戏“Farkle”。老师给我们提供了一个框架，我一直卡在实现roll功能上。我的目标是使用 rand 函数随机生成一个介于 1 - 6 之间的数字，并将该值放在 vector RolledDice 中(我不需要 rand 函数的帮助)我只需要帮助将 RolledDice 的值设置为等于什么rand 函数产生。

问题是Game.cpp中的Roll()函数

• 部分问题是试图将 rolledDice 设置为 int 值。
• 另一个问题是访问 public 类中的结构。
• 如何使用 push_back 函数将这些值填充到 vector 中？

在我的 Game.cpp 中我有:

Game::Die::Die ()
{
// This function will: Initalize the value of the dice

    pips = 0;
    selected = false;
    used = false;
}

ostream & operator << (ostream & outs, const Game::Die & D)
{
// This function will: output the score
    return outs;
}

Game::Game (const string & T) 
{
// This function will: initializer the random variables

    title = T;
//  srand (0);
    srand (time (NULL));

}

Game::~Game ()
{


}

void Game::Init ()
{

    gameState = GO;
    whoseTurn = NONE;
    humanOnBoard = false;
    aiaOnBoard = false;
    humanScore = 0;
    aiaScore = 0;
    lastTurn = false;
}

void Game::Instructions (ostream & outs)
{


    outs << endl << "Welcome to " << title << endl;
    outs << "The goal of this game is to accumulate 5000" 
         << " points before your opponent." << endl;
    outs << "In this case, this program is your opponent." << endl;
    outs << "You must score 500 points in a single turn to" 
         << " start accumulating points." << endl << endl;
    sleep (1);

}

void Game::StartTurn ()
{


    if (whoseTurn == NONE || whoseTurn == AIA)
    {
        whoseTurn = HUMAN;
        Roll();
    }
    else 
    {
        whoseTurn = AIA;
        turnDone = false;
        numToRoll = MAX_DICE;
        savedDice.clear ();
        subTotal = 0;
        turnTotal = 0;
        Roll();
    }
}



bool Game::Enter (char selection, ostream & outs)
{
// This function will:

    switch (selection)
    {
        case 'i': Instructions (outs);
            break;
        case 'r': 
            SaveSelected();
            Roll ();
            break;
        case 's': 
            SaveSelected();
            SaveScore();
            break;
        case 'q': 
            gameState = QUITTER;
            turnDone = true;
            break;
        default:
        {

            int which = selection - 'a';
            if (which < 0 || which >= rolledDice.size())
                return false;
            rolledDice[which].selected = !rolledDice[which].selected;
        }
    }
    return true;
}

void Game::Roll () // Roll function
{
    rolledDice.push_back(Game::Die.pips); // **This is my issue**
}

我试过:

void Game::Roll () // Roll function
    {
        int numRolled = rand()%6 + 1;
        rolledDice.push_back(numRolled) // **This is my issue**
    }

还有:

void Game::Roll () // Roll function
    {
        int numRolled = rand()%6 + 1;
        rolledDice.pips.push_back(numRolled) // **This is my issue**
    }

这不起作用，因为 rolledDice 无法转换为 int

还有很多其他的东西我不可能放在这篇文章中，我只是认为这些是最接近说明我正在尝试做的事情的东西。

在我的 Game.h 中我有:

class Game
{
    public:
        Game (const string & T);
        ~Game ();
        void Init ();
        void Instructions (ostream & outs);
        void StartTurn ();
        friend ostream & operator << (ostream & outs, const Game & G);
        bool Enter (char selection, ostream & outs);
        bool TurnDone ();
        int AIAPlayer (ostream & outs);
        bool Done ();
        void Message (ostream & outs);

        struct Die
        {
                Die ();
                friend ostream & operator << (ostream & outs, const Die & D);
                int pips;
                bool selected;
                bool used;
        };

    private:
        void Roll ();
        int CalculateScore (vector <Die> & dice);
        void SaveSelected ();
        void SaveScore ();

        string title;
        vector <Die> rolledDice; // Dice Rolled
        vector <Die> remainingDice; // Will take out dice saved
        vector <Die> selectedDice; // Will temporarily save the selected dice
        vector <Die> savedDice; // Will save the dice
        state_types gameState;
        player_type whoseTurn;
        bool turnDone;
        int numToRoll;
        int rolledScore;
        int subTotal;
        int turnTotal;
        bool humanOnBoard;
        bool aiaOnBoard;
        int humanScore;
        int aiaScore;
        bool lastTurn;
};

如果您需要发布更多信息就可以了。非常感谢任何帮助。

Answer 1

通过创建构造函数

Die::Die(int pips)

您正在创建一个将用作隐式类型转换的构造函数。这极大地简化了添加到 vector 的语法。要没有这个，你需要关键字 explicit。它有时会在您的程序中产生不直观的语义。

一个简单的概念证明:

#include <iostream>
#include <vector>
struct Die{
    Die(int pips):pips(pips){}

    int pips;
};

std::vector<Die> tosses;

int main(void)
{
    tosses.push_back(2); // Works because of the converting constructor.
    tosses.push_back(2);
    tosses.push_back(1);
    tosses.push_back(2);

    for(auto toss:tosses){                                                                                                             
       std::cout << toss.pips;
    }

}

同时考虑 http://en.cppreference.com/w/cpp/numeric/random/uniform_int_distribution用于优雅和正确的掷骰子。我见过的大多数反对 std::rand 的论点都包含掷骰子。