Cast string object to istringstream

#include <iostream>
#include <fstream>
#include <string>
#include <vector>
#include <algorithm>

void reverse_words(const std::string &file) {
    std::ifstream inFile { file };
    std::vector<std::string> lines;
    if(static_cast<bool>(inFile)) {
        std::string line;
        while(std::getline(inFile, line, '\n')) {
                lines.push_back(line);
        }

    std::vector<std::string> reverse_line;
    std::string word;
    for(auto line: lines) {
        while(std::getline(line, word, ' '))
            reverse_line.push_back(word);

    }

    }
}

int main(int argc, char ** argv) {
    if(argc == 2) {
        reverse_words(argv[1]);
    }
}

In the last for loop of my program I would like to read in a word from a line, the line is a string so this does not match the getline() function definition. How can I cast the line to a stringstream so that I can use it for reading just like a file ?

Please ignore the logic of the program at the moment, it is not complete, my question is C++ specific.