数据输出奇怪的数字到文件，MAP c++

Question

在使用 cin 输入某些值后，我正在尝试覆盖文件中的数据。我面临的问题是，应该修改文件的函数实际上并没有正确执行。

这是场景，我使用注册函数添加这些数据

代码：

// register a student to the system
void Student::registerStudent(string name, int studentNo, char gender) {
        outStream.open("StudentRecord.txt", ios_base::app);
        outStream << left << setw(15) << studentNo << setw(15) << gender << right << name << endl; 
        outStream.close();
}

我添加了 3 次数据，我得到了

    Batman   11  M   
    BatGirl  22  F
    Joker    33  M

现在问题来了，我尝试通过添加额外的主题分数来修改 蝙蝠侠 行

我想要的结果：

    Batman   11  M   100  22  55 22  33
    BatGirl  22  F
    Joker    33  M

名字后面的数字是科目分数。

但是，当我运行程序来修改特定行时，我得到了这个

BatGirl        22             F              -858993460     -858993460          -858993460     -858993460     -858993460
Batman         11             M              12             86                          44             24             55
Joker          33             M              -858993460     -858993460          -858993460     -858993460     -858993460

这里是具体行修改的代码

//  Function to modify a student's exam scores.
    void Student::modifyScore(string newName, int newIndian, int newEnglish, int newMath, int newHistory, int newMoral) {


    map<string, tuple<int, char,int, int, int, int, int> > data;

    // Read file and fill data map
    ifstream studentRec("StudentRecord.txt");
    string line;

    while (getline(studentRec, line))
    {
       string name;
       int studentNo;
       char gender;
       int indian, english, math, history, moral;
       stringstream ss(line);
       ss >> name >> studentNo>> gender>> indian >> english >> math >> history >> moral;
       data[name] = make_tuple(studentNo, gender,indian, english, math, history, moral);

    }

    studentRec.close();
    // Modify data


    auto it = data.find(newName) ; // gets current student record from the map
    if (it == data.end()) // student not in map, that's an error
     return ;
    // now it->second holds your student data
    // an auto here could be better, but we want to be sure of type
    auto studentNo = get<0>(it->second) ;
    auto gender = get<1>(it->second) ;

     data[newName] = make_tuple(studentNo, gender, newIndian,newEnglish, newMath, newHistory, newMoral);


    // Open same file for output, overwrite existing data
    ofstream ofs("StudentRecord.txt");

    for (auto entry = data.begin(); entry != data.end(); ++entry)
    {
        tie(studentNo, gender, newIndian,newEnglish, newMath, newHistory, newMoral) = entry->second;
        //int average = averageScore(newIndian,newEnglish, newMath, newHistory, newMoral);

        ofs << left <<  setw(15) << entry->first << setw(15) << studentNo << setw(15) << gender << setw(15) << newIndian << setw(15) << newEnglish << setw(15) << right << newMath << setw(15) << newHistory << setw(15) <<  newMoral << endl;
    }
    ofs.close();


}

为了清楚起见，modifyScore 的参数是

newName --> is to find the name in the file
newIndian --> Subject scores
newEnglish --> Subject scores
newMath --> Subject scores
newHistory --> Subject scores
newMoral --> Subject scores

请指出我犯错的地方。谢谢！

Answer 1

问题是

   stringstream ss(line);
   ss >> name >> studentNo>> gender>> indian >> english >> math >> history >> moral;

当您遇到像Batman 11 M 这样的3 字行时，表达式ss >> indian will fail and activate the failbit。这意味着 indian 之后的所有变量都不会被修改。就目前而言，它们是未初始化的，这解释了您获得的值的随机性。

现在要解决这个问题，您应该检测特定行中的列数，即number of words in the string，这样您就可以将未修改行的状态恢复到之前的状态。

unsigned int countWordsInString(std::string const& str);

bool fullrecord(std::string const& str)
{
   return countWordsInString(str) == 8;
}

map<string, tuple<int, char,int, int, int, int, int, bool> > data; //added bool
stringstream ss(line);
bool hasGrades = fullrecord(line);
if(hasGrades )
    ss >> name >> studentNo>> gender>> indian >> english >> math >> history >> moral;
else
    ss >> name >> studentNo>> gender;
data[name] = make_tuple(studentNo, gender,indian, english, math, history, moral, hasGrades);

现在使用布尔值来决定是否保存带或不带等级的行