c++ - 构造函数内的默认参数错误-C++

Question

This question already has an answer here:

error: default argument given for parameter 1

(1个答案)


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我正在制作一个Connect 4程序，并且想创建一个处理开发板使用的类。但是，我希望板的默认“大小”为宽度7和高度6，因此我尝试使用默认参数。在没有太多信息可以帮助我的情况下，我总是遇到同样的错误。

header :

#include <iostream>
class Board{
    public:
        //constructor
        Board(int width=7, int height=6);
        //deconstructor
        ~Board();
        //copy constructor
        Board(const Board & toCopy);

        //create the board
        void ResetBoard();

        //print current board
        void PrintBoard();

    protected:
        int width;
        int height;
        int ** field = nullptr;
};

董事会定义:

#include "Board.hpp"

Board::Board(int w=7, int h=6){//<--L()()K Error - FIX ME
    width = w;
    height = h;
    /*ALLOCATE MEMORY FOR 2D ARRAY*/
    field = new int*[height];
    for(int i = 0; i < height; ++i){//skip the first line since it is already filled
        field[i] = new int[width];
    }

    /*ITERATE THROUGH ARRAY AND INPUT 0*/
    for(int i = 0; i < height; ++i){
        for(int j = 0; j < width; ++j){
            field[i][j] = 0;
        }
    }
}

void Board::PrintBoard(){
    /*PRINT BOARD*/
    for(int i = 0; i < height; ++i){
        std::cout<<"\n";
        for(int j = 0; j < width; ++j){
            std::cout<<field[i][j]<<" ";
        }
    }    
}

错误讯息:

Board.cpp:3:30: error: default argument given for parameter 1 of ‘Board::Board(int, int)’ [-fpermissive]
 Board::Board(int w=7, int h=6){
                              ^
In file included from Board.cpp:1:0:
Board.hpp:5:9: note: previous specification in ‘Board::Board(int, int)’ here
         Board(int width=7, int height=6);
         ^~~~~
Board.cpp:3:30: error: default argument given for parameter 2 of ‘Board::Board(int, int)’ [-fpermissive]
 Board::Board(int w=7, int h=6){
                              ^
In file included from Board.cpp:1:0:
Board.hpp:5:9: note: previous specification in ‘Board::Board(int, int)’ here
         Board(int width=7, int height=6);
         ^~~~~

我通常不使用默认参数，但我认为这是一个不错的设计选择。任何帮助是极大的赞赏!

最佳答案

您需要从声明中删除默认参数，并将它们仅保留在定义中:

宣言:

Board(int width, int height);

定义:

Board::Board(int w = 7, int h = 6) {//<--L()()K Error - FIX ME
    width = w;
    height = h;
    /*ALLOCATE MEMORY FOR 2D ARRAY*/
    field = new int* [height];
    for (int i = 0; i < height; ++i) {//skip the first line since it is already filled
        field[i] = new int[width];
    }

    /*ITERATE THROUGH ARRAY AND INPUT 0*/
    for (int i = 0; i < height; ++i) {
        for (int j = 0; j < width; ++j) {
            field[i][j] = 0;
        }
    }
}

主要:

int main()
{
    Board board;
    board.PrintBoard();
}

结果:

0 0 0 0 0 0 0
0 0 0 0 0 0 0
0 0 0 0 0 0 0
0 0 0 0 0 0 0
0 0 0 0 0 0 0
0 0 0 0 0 0 0

关于c++ - 构造函数内的默认参数错误-C++，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/62356042/

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Answer 1

您需要从声明中删除默认参数，并将它们仅保留在定义中:

宣言:

Board(int width, int height);

定义:

Board::Board(int w = 7, int h = 6) {//<--L()()K Error - FIX ME
    width = w;
    height = h;
    /*ALLOCATE MEMORY FOR 2D ARRAY*/
    field = new int* [height];
    for (int i = 0; i < height; ++i) {//skip the first line since it is already filled
        field[i] = new int[width];
    }

    /*ITERATE THROUGH ARRAY AND INPUT 0*/
    for (int i = 0; i < height; ++i) {
        for (int j = 0; j < width; ++j) {
            field[i][j] = 0;
        }
    }
}

主要:

int main()
{
    Board board;
    board.PrintBoard();
}

结果:

0 0 0 0 0 0 0
0 0 0 0 0 0 0
0 0 0 0 0 0 0
0 0 0 0 0 0 0
0 0 0 0 0 0 0
0 0 0 0 0 0 0