零在类构造函数C ++中初始化多维数组

Question

Is there a way (with C++11) to zero-initialize a multidimensional array in a class constructor?

Does this initialize the whole array to zero or just the first dimension?

class Example
{
public:
    int array[100][100];

    Example():array{}
    {
    };
};

Lastly, will this work with enumerated types?

Answer 1

Value-initialization for an array will value-initialize each element in the array. You have an array of arrays, so each element (an array) will be value-initialized. From there, return to the first sentence of this answer for what happens to each array.

The answer to your second question, regular enumerations are scalars, and as such are value-initialized, just like your int values in your array, which is to say they're zero-initialized . That may be problematic if you have an enum without a 0-value representation:

#include <iostream>

enum EnumStuff
{
    one = 1,
    two = 2,
    three = 3
};

int main()
{
    EnumStuff arr[10][10]{};
    for (auto const&x : arr)
    {
        for (auto y : x)
            std::cout << static_cast<int>(y) << ' ';
        std::cout << '\n';
    }
}

There is no 0-value in EnumStuff . Just something to keep in mind. A switch looking for only those three values, for example, will be sorely-disappointed (and shortly thereafter, likely you with it).

Best of luck

Answer 2

多维数组的值初始化（即使用{} ）值初始化所有元素，因此所有10000个元素的值都为0。