How to make threads work with c++ class?

Question

C++ / C#

It is necessary to look for numbers greater than the one entered in the matrix so that a separate thread is allocated for each row of the matrix.
My code doesn't work with my class and throws a huge error that I can't figure out. (there is no problem when working with ordinary types, such as int primes)

main.cpp

#include "Matrix.h"

int main() {
    std::int32_t number = 5;
    Matrix matrix;
    matrix.printMatrix();
    
    std::cout << matrix.findMoreThanNumber(number) << std::endl;
    return 0;
}

Matrix.h

#ifndef LAB9_MATRIX_H
#define LAB9_MATRIX_H
#include <iostream>
#include <ctime>
#include "mingw.thread.h"
#include <chrono>
#include <vector>


class Matrix {
 public:
    Matrix();
    void printMatrix() const;
    void findNumberInRow(const std::vector<std::int32_t> &row, const std::int32_t number);
    std::int32_t findMoreThanNumber(const std::int32_t number);

 private:
    std::int32_t rows, cols, count;
    std::vector<std::vector<std::int32_t>> matrix;
};

#endif  // LAB9_MATRIX_H

Matrix.cpp

#include "Matrix.h"

Matrix::Matrix() : rows(5), cols(5), count(0), matrix(rows) {
    srand(time(NULL));

    for (std::vector<int>& col : matrix)
    {
        col = std::vector<int>(cols);
    }

    for (std::size_t i = 0; i < rows; i++) {
        for (std::size_t j = 0; j < cols; j++) {
            matrix[i][j] = rand() % 10;
        }
    }
}

void Matrix::printMatrix() const {
    for (std::size_t i = 0; i < rows; i++) {
        for (std::size_t j = 0; j < cols; j++) {
            std::cout << matrix[i][j] << " ";
        } 
        std::cout << std::endl;
    }
    std::cout << std::endl;
}

void Matrix::findNumberInRow(const std::vector<std::int32_t> &row, const std::int32_t number) {
    std::cout << "Thread ID = " << std::this_thread::get_id() << " for" << std::endl;
    for (std::size_t i = 0; i < rows; i++) {
        std::cout << row[i] << " ";
        if (row[i] > number) {
            count++;
        }
    }
    std::cout << std::endl;
}


std::int32_t Matrix::findMoreThanNumber(std::int32_t number) {
    std::vector<std::thread> threads;
    for (std::size_t i = 0; i < cols; i++) {
        std::thread thread(findNumberInRow, matrix[i], number);
        threads.push_back(std::move(thread));
    }

    for (std::thread& thread : threads) {
        thread.join();
    }

    return count;
}

Mistakes

Что бы загрузить сюда не хватило места, поэтому загружаю так.
https://pastebin.com/PNLMbSeA

Answer 1

You are passing a non-static class method to std::thread. It cannot be passed as a normal function. It can only be called on some object. Where will thread take this object?
There are 2 options - pass a lambda that will capture this and call the object's method on it.
Or, as shown here , pass there &Matrix::findNumberInRowwith the first argument this.