在 std::getline 和 std::cin 在 while 循环期间陷入循环

Question

So I'm new to C++ and I'm supposed to get a vector in integers from stdin. I tried using std::cin and std::getline and other functions, but everytime I try entering a sentinel (eg not an integer) or when there is a "count" variable that reaches an increment, I end up in a hung state. I can enter inputs, but no more print statements (eg "std::cout << "added") appear after the count has reached. I'm not sure what went wrong with the std::cin.

std::vector<int> Game::getIds() {
    std::vector<int> cards; 
    int x =0 ;  
    std::string mystr; 
    bool keepGoing = true; 
    int count = 0; 
    while (keepGoing) {
        std::getline(std::cin, mystr); 
        std::stringstream sstream(mystr); 
        while (sstream >> x) { 
            std::cout << "added" << x << std::endl; 
            cards.push_back(x); 
        }
        if (std::cin.fail()) {
            keepGoing = false; 
            std::cout <<"fail";
            std::cin.clear(); 
            std::cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n'); 
            return cards;
        }
        ++count; 
        if (count == 5) return cards; 
    } 
    return cards; 
}

Answer 1

cin controls input from a stream buffer, which put your input characters in a stream buffer, then it was passed to getline . cin ends input when you signaled EOF with Ctrl+D , Ctrl+Z , or Enter . See this link detecting end of input with cin .

getline extracts characters from input and appends them to str until it meet one of the end conditions, in your situaton the end condition is the endline character '\n' , because the default delimeter is the endline character. You may define your own delimeter getline(intput, str, $your_delemeter) , and do a little experiment.