solved the problem of C array mapping failure during reflection

[huqin-RM]

it's seem solved the problem of C array mapping failure during reflection

template<typename T>
void ProcData(const json& j, std::vector<T> &v, int back_size)
{
    for(auto it : j)
    {
        if(it.is_array())
        {
            ProcData(it, v, back_size);
        }else if(it.is_string())
        {
            std::string tmp = it.get<std::string>();
            if(tmp == "")
            {
                for(int i = 0; i < back_size; i++)
                {
                    v.push_back('\0');
                }
                continue;
            }
            v.insert(v.end(), tmp.begin(), tmp.end());
            while (v.size() % back_size != 0) {
                v.push_back('\0');
            }
        }
        else
        {
            T tmp = it.get<T>();
            v.emplace_back(tmp);
        }
    }
}

template<typename T>
void PrcoArray(T value, const json& j, void *c, int size, int front_size, int back_size) {
    std::vector<T> data;
    ProcData(j, data, back_size);
    memcpy(c,data.data(), size);
}

template<typename T>
void PrcoArray(T arr[], const json& j, void *c, int size, int front_size, int back_size) {
    back_size = front_size / sizeof(arr[0]);
    PrcoArray(arr[0], j,c, size, sizeof(arr[0]), back_size);
}

namespace nlohmann
{
template<typename T, size_t N, size_t M>
void from_json(const json& j, T (&c)[N][M]) {
    PrcoArray(c, j, c, sizeof(c), sizeof(c), 0);
}

template<typename T, size_t N>
void from_json(const json& j, T (&a)[N]) {
    PrcoArray(a, j, a, N, N, 0);
}

}

class Der2
{
public:
    virtual void test()
    {

    }
    int a;
    int b;
    double c[4][5][6][7]{{{1998}},{{1999}}};
    char c1[4];
    char c2[4][4][4]{0};
public:
    NLOHMANN_DEFINE_TYPE_INTRUSIVE(Der2,a,b,c,c1,c2)

The multidimensional arrays in the above code, including char arrays, can be reflected normally.Can the official test be carried @gregmarr @nlohmann

The following is the test code

int main() {

    json test;
    Der2 a;
    a.a = 1000;
    a.b = 10000;
    a.c[0][0][0][0] = 951;
    a.c[1][0][0][0] = 950;
    a.c1[0] = 'q';
    a.c1[1] = 'w';
    a.c1[2] = '\0';

    a.c2[0][0][0] = 'Q';
    a.c2[0][0][1] = 'W';
    a.c2[0][0][2] = '\0';

    a.c2[1][0][0] = 'T';
    a.c2[1][0][1] = 'Y';
    a.c2[1][0][2] = '\0';

    test = a;
    Der2 a1;
    a1 = test;
    json test2;
    test2 = a1;

    std::cout << test << std::endl;
    std::cout << test2 << std::endl;
    std::cout << a1.c[0][0][0][0] << " " << a1.c[1][0][0][0] << " " << a1.c1[0] << " " << a1.c1[1]<< std::endl;
    std::cout << a1.c2[0][0] << " " << a1.c2[1][0] << std::endl;

    return 0;
}

[nlohmann]

Thanks for sharing your from_json overloads for multidimensional and char arrays, and for the runnable test case - it's a nice complement to the multidimensional array support added in 3.12.0. We can't commit to adding this exact pattern as an official test, but a PR with a focused unit test would be very welcome.

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This reply was drafted by Claude Code on behalf of @nlohmann, as part of a review of open discussions.