Can I initialize a static c++ class member which is a multidimensional array with a function?

Question

I have a class that follows as such:

class foo{
  static std::string L[256][256];
  public:
    //rest of class
};

std::string foo:L[256][256];

I would like to initialize L using a function such as the following.

void begin_l(std::string L[256][256]){
  //initialization code
}

I have tried making a function that returns L to accomplish this, but received the error function cannot return array type 'std::string [256][256]'

How could I go about doing this?

Answer 1

You can do it with a directly invoked lambda function :

#include <iostream>
#include <array>
#include <string>
#include <iomanip>

// add an alias for readability
using array_2d_of_string_t = std::array<std::array<std::string, 4>, 4>;

class foo 
{
public:
    //rest of class
    static array_2d_of_string_t L;
};

// initialize static variables with a directly
// invoked lambda function. The lambda function will be a nameless
// function so it can only be used to initialize this variable.
array_2d_of_string_t foo::L = []
{
    std::size_t count{ 0ul };
    array_2d_of_string_t values{};

    // loop over all rows in the 2d array
    for (auto& row : values)
    {
        // loop over all the values in the array and assign a value
        for (auto& value : row)
        {
            value = std::to_string(count++);
        }
    }

    return values;
}();

int main()
{
    for (auto& row : foo::L)
    {
        for (auto& value : row)
        {
            std::cout << std::quoted(value) << " ";
        }
        std::cout << "\n";
    }

    return 0;
}