'this'不能用于常量表达式错误 (C++)

'this' cannot be used in a constant expression error (C++)

本文关键字：错误 C++ 用于 this 不能常量表达式更新时间：2023-10-16

all。我有一个类定义如下：

class Board {
    int columns, rows;
    bool board[10][10];
public:
    Board(int, int);
    void nextFrame();
    void printFrame();
};

我的void nextFrame()一直给我[rows][columns]的错误，因为它们都"this"不能在常量表达式中。我如何重新定义它，使其发挥作用？我理解这个错误。函数的定义如下，错误出现在以下代码示例的第3行。

void Board::nextFrame() {
        int numSurrounding = 0;
        bool tempBoard[rows][columns];
        for (int i = 0; i < rows; i++)
        {
            for (int j = 0; j < columns; j++)
            {
                if ((i + 1) < rows && board[i + 1][j] == true)
                {
                    numSurrounding++;
                }
                if ((i - 1) >= 0 && board[i - 1][j] == true)
                {
                    numSurrounding++;
                }
                if ((j + 1) < columns && board[i][j + 1] == true)
                {
                    numSurrounding++;
                }
                if ((j - 1) >= 0 && board[i][j - 1] == true)
                {
                    numSurrounding++;
                }
                if ((i + 1) < rows && (j + 1) < columns && board[i + 1][j + 1] == true)
                {
                    numSurrounding++;
                }
                if ((i + 1) < rows && (j - 1) >= 0 && board[i + 1][j - 1] == true)
                {
                    numSurrounding++;
                }
                if ((i - 1) >= 0 && (j + 1) < columns && board[i - 1][j + 1] == true)
                {
                    numSurrounding++;
                }
                if ((i - 1) >= 0 && (j - 1) >= 0 && board[i - 1][j - 1] == true)
                {
                    numSurrounding++;
                }
                if (numSurrounding < 2 || numSurrounding > 3)
                {
                    tempBoard[i][j] = false;
                }
                else if (numSurrounding == 2)
                {
                    tempBoard[i][j] = board[i][j];
                }
                else if (numSurrounding == 3)
                {
                    tempBoard[i][j] = true;
                }
                numSurrounding = 0;
            }
        }
        for (int i = 0; i < rows; i++)
        {
            for (int j = 0; j < columns; j++)
        {
            board[i][j] = tempBoard[i][j];
        }
    }
}

您需要使用STL中的集合。

下面是一个嵌套矢量以获得棋盘的例子：

#include <vector>
#include <iostream>
using namespace std;
class Board {
    int columns, rows;
    vector<vector<bool>> board;
public:
    Board(int x, int y) : board(vector<vector<bool>>(x, vector<bool>(y))) {
    }
    void nextFrame() {
        // Fill in
    }
    void printFrame() {
        // Fill in
    }
    size_t xdim() {
        return board.size();
    }
    size_t ydim() {
        if (board.size() == 0) {
            return 0;
        }
        return board.at(0).size();
    }
};
int main() {
    Board b(10, 20);
    cout << "Made the board" << endl;
    cout << "X: " << b.xdim() << endl;
    cout << "Y: " << b.ydim() << endl;
}

您可以在此处和此处了解board(vector<vector<bool>>(x, vector<bool>(y)))的成员初始化语法。