writing/reading to/from a dynamic_bitset in a file c++

So I am converting the bit string to a vector of type int and then pushing the elements of vector in dynamic_bitset object and writing that object into file. Here is my code.

#include <iostream>
#include <boost/dynamic_bitset.hpp>
#include <fstream>
#include <streambuf>
#include "Utility.h"
using namespace std;
using namespace boost;

class BitOperations {
private:
    string data;
    int size;
    dynamic_bitset<unsigned char> Bits;
    string fName;

public:
    // BitOperations(dynamic_bitset<unsigned char> b){
    //     Bits = b;
    //     size = b.size();
    // }

    // BitOperations(dynamic_bitset<unsigned char> b, string fName){
    //     Bits = b;
    //     this->fName = fName;
    //     size = b.size();
    // }

    BitOperations(string data, string fName){
        this->data = data;
        this->fName = fName;
    }

    void writeToFile(){
        if (data != ""){
            vector<int> bitTemp;
            bitTemp = extractIntegers(data);
            for (int i = 0; i < bitTemp.size(); i++){
                Bits.push_back(bitTemp[i]);
            }
            // for (int i = 0; i < bitTemp.size(); i++){
            //     cout << Bits[i] << " ";
            // }
            // cout << endl;
        }
        ofstream output(fName, ios::binary);
        ostream_iterator<char> osit(output);
        to_block_range(Bits, osit);
    }

    dynamic_bitset<unsigned char> readFromFile(){
        int count = 0;
        ifstream t(fName);
        string str((std::istreambuf_iterator<char>(t)),
                 std::istreambuf_iterator<char>());
        cout << str << endl;
        dynamic_bitset<unsigned char> b;
        int bitLen = str.length() * 8;
        for (int i = 0; i < str.length(); i++){
            for (int j = 0; j < 8; ++j){
                bool isSet = str[i] & (1 << j);
                b.push_back(isSet);
            }
        }

        return b;
    }
};

Here is the code for converting bit string into vector type of integer.

vector<int> extractIntegers(string s){
    stringstream stream;
    stream << s;

    string tmp;
    int flag;
    vector<int> nums;

    while (!stream.eof()){
        stream >> tmp;
        if (stringstream(tmp) >> flag){
            nums.push_back(flag);
        }
        tmp = "";
    }
    return nums;
}

I tried to print the elements of "Bits" but it does not print anything and also has length of 1. What am I doing wrong?