错误C2440：“ =”：无法从“ int *”转换为“ int **”

Question

#ifndef _grid_h
#define _grid_h

#include<string>

using namespace std;

template<typename T>
class grid{
    T** main;

public:

    grid<T>(){}


    grid<T>(int col, int row){  
        main = new T[col];          //<-this line gives me error C2440:
                                    //'=' : cannot convert from 'int *' to 'int **'
        for(int i =0;i<col;i++)
            main[i]=new T[row];
    }
};

#endif

I want to create my own version of the Grid class. Basically I want to save the information in a 2 dimensional array of T. I think this is the most efficient way to do it. Now How can I get around this error?

Answer 1

Allocate an array of correct type: use main = new T*[col]; instead of main = new T[col]; .

Answer 2

It would need to be

main = new T*[col];

Because main is an array of pointers to T . But there are better ways to create a two-dimensional array, for example

std::vector<std::vector<T>> main(col, std::vector<T>(row));

Answer 3

The answer is in your last code line:

main[i]=new T[row];

For that to work, main[i] needs to be a pointer. But you tried to create main as a new T[col] - an array of T s. It needs to be an array of pointers-to- T .

main = new T*[col]; // Create an array of pointers