对象构造函数的C ++ 2D数组

问题描述：

在我的Dev C ++中，我试图创建一个像Grid一样的2D Array类。
但是问题之一是我不确定该对构造函数做什么。

In my Dev C++, I am trying to create a 2D Array class that acts like a Grid. But one of the problem is I am unsure what do for the constructor.

当我尝试编译时，出现以下错误：
在构造函数'Grid :: Grid（int，int）'中：
'sqaures'不是类型
'yPos'不能出现在常量表达式
中[Build Error] [grid。 o]错误1

When I try to compile, I get the following errors: In constructor 'Grid::Grid(int,int)': 'sqaures' is not a type 'yPos' cannot appear in a constant-expression [Build Error] [grid.o] Error 1

以下是头文件：

#ifndef GRID_H
#define GRID_H

using namespace std;

class Grid
{
      public:

      Grid(int xPos, int yPos);
      // Constructor
      // POST: Creates the squares of grid; (x,y) coordinates

      private:

      int squares;
      //2D Array
      //the squares; (x,y) coordinates of the grids      
};

#endif

这是网格功能的.cpp文件.h

And heres the .cpp file for the functions of grid.h

#include <iostream>
#include "grid.h"

using namespace std;

Grid::Grid(int xPos, int yPos)
{
    squares = new squares[xPos][yPos];
    //Trying to make squares into a 2D array, and turn the values into the arguments
    //into the the x,y coordinates 
}

.cpp文件中的构造函数不起作用，我不确定该怎么做。有人有任何解决方案吗？

My constructor in the .cpp files doesn't work and I'm unsure what to do. Does anyone have any solutions?

答

您的代码有一些问题。
首先，您的成员变量 squares应为指向int的指针，而不是 int ：

There are a few problems with your code. First of all, your member variable "squares" should be a pointer to an int, not an int:

int *squares;

然后，以下行将出现错误：

Then, the following line will give an error:

squares = new squares[xPos][yPos];

您真正需要的是2D数组的内存块：

What you really need is a block of memory for the 2D array:

squares = new squares[xPos * yPos];

此外，您还应将此数组的尺寸保存在成员变量中（例如 sizeX和 sizeY）

Also, you should save the dimensions of this array in member variables (e.g., "sizeX" and "sizeY" )

现在，您有一块内存，可以容纳2D正方形数组。我通常会重载（）运算符以访问此数组中的元素：

Now, you have a block of memory which will hold a 2D array of squares. I usually overload the () operator for accessing an element in this array:

int &Grid::operator() (int x, int y)
{
      // you can check array boundaries here
      return squares[y + sizeX*x];
}

如果您对运算符有疑问，只需创建一个成员函数即可：

If you have problems with the operator stuff, just create a member function instead:

int Grid::get(int x, int y)
{
     // check array bounds
     return squares[y + sizeX*x];
}
void Grid::set(int x, int y, int value)
{
     // check array bounds
     squares[y + sizeX*x] = value;
}

最后，您需要一个析构函数来释放内存：

Finally, you need a destructor to free the memory:

Grid::~Grid()
{
     delete [] squares;
}

这就是我喜欢这样做的方式（ C类）。在另一个答案中，David Norman提供了一种很好的标准C ++方式来实现您的类。

This is how I like to do it (the "C-with-classes" style). In another answer, David Norman gives a good "Standard C++" way of implementing your class.

对象构造函数的C ++ 2D数组

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