Reading from CSV file with C++ - c++

Question

I was trying to read the records from a CSV file. This code is froom GeeksforGeeks. I tried compiling it. Then when I try to run it terminates with an exception
void read_record()
{
// File pointer
fstream fin;
// Open an existing file
fin.open("reportcard.csv", ios::in);
// Get the roll number
// of which the data is required
int rollnum, roll2, count = 0;
cout << "Enter the roll number "
<< "of the student to display details: ";
cin >> rollnum;
// Read the Data from the file
// as String Vector
vector<string> row;
string line, word, temp;
while (fin >> temp) {
row.clear();
// read an entire row and
// store it in a string variable 'line'
getline(fin, line);
// used for breaking words
stringstream s(line);
// read every column data of a row and
// store it in a string variable, 'word'
while (getline(s, word, ',')) {
// add all the column data
// of a row to a vector
row.push_back(word);
}
// convert string to integer for comparision
roll2 = stoi(row[0]);
// Compare the roll number
if (roll2 == rollnum) {
// Print the found data
count = 1;
cout << "Details of Roll " << row[0] << " : \n";
cout << "Name: " << row[1] << "\n";
cout << "Maths: " << row[2] << "\n";
cout << "Physics: " << row[3] << "\n";
cout << "Chemistry: " << row[4] << "\n";
cout << "Biology: " << row[5] << "\n";
break;
}
}
if (count == 0)
cout << "Record not found\n";
}
Program terminates with a message
terminate called after throwing an instance of 'std::invalid_argument'
what(): stoi"

Answer 1

your current error is that row[0] is not a string. stoi expects a string. invalid argument means the value you gave a function inside the parenthesis is not the value that the computer expects. i might try printing the variable of one line and checking the type with
cout << typeid(row[0]).name.()
It also is best practice to do things incrementally when coding (walk before you can run.) try reading in one cell and closing if youre struggling with that. then one line. then multiple lines. its easy enough to comment out lines of code. many text editor even have a hotkey to comment out lines of code. try googling
block comment hotkey [your text editor name]

Answer 2

void read_record()
{
// File pointer
fstream fin;
// Open an existing file
fin.open("reportcard.csv", ios::in);
// Get the roll number
// of which the data is required
int rollnum, count = 0;
cout << "Enter the roll number "
<< "of the student to display details: ";
cin >> rollnum;
ostringstream roll2;
roll2 << rollnum;
string roll = roll2.str();
//cout << roll;
// Read the Data from the file
// as String Vector
vector<string> row;
string line, word, temp;
while (!fin.eof()) {
row.clear();
// read an entire row and
// store it in a string variable 'line'
getline(fin, line);
// used for breaking words
stringstream s(line);
// read every column data of a row and
// store it in a string variable, 'word'
while (getline(s, word, ',')) {
// add all the column data
// of a row to a vector
row.push_back(word);
}
// convert string to integer for comparision
//roll2 = stoi(row[0]);
//cout << row[0] << row[1] << row[2] << row[3] << row[4] << row[5] << "\n";
// Compare the roll number
if (roll == row[0]) {
// Print the found data
count = 1;
cout << "Details of Roll " << row[0] << " : \n";
cout << "Name: " << row[1] << "\n";
cout << "Maths: " << row[2] << "\n";
cout << "Physics: " << row[3] << "\n";
cout << "Chemistry: " << row[4] << "\n";
cout << "Biology: " << row[5] << "\n";
break;
}
}
if (count == 0)
cout << "Record not found\n";
}