从文本文件中读取字符串和浮点数

Question

I realize there are similar questions to this however, those solutions seem to only work if a group of data is on the same line.

I have some data structured in text file like so:

<string student name>
<string course>
<float mark>
...

Every 3 lines is a new student, with a total of 6 students. My code works until it gets to the part where it assigns a mark, which I need to read in as a float , everything else is a string.

I;ve found that getline() won't do this for me, wondering what is the best way to work with mixed types from a text file?

#include <iomanip>
#include <ios>
#include <iostream>
#include <iterator>
#include <list>
#include <fstream>

struct Student {
    std::string name;
    std::string course;
    std::string grade;
    float mark;
};

int main() {

    Student students [6];
    std::string filename = "data.txt";
    std::ifstream file(filename);

    int i = 0;
    
    while(getline(file, students[i].name))
    {
        getline(file, students[i].course);
        getline(file, students[i].mark);
        
        if (students[i].mark > 89.5) {
            students[i].grade = "HD";
        } else {
            students[i].grade = "PASS";
        }
        
        ++i;
    }
    
    return 0;
}

Answer 1

I had the requirement to get the data line by line, assuming every three lines was a new student. My next requirement was that the third line would be a float but getline() reads in as a string.

My solution was to just create a temporary variable to take the string and then convert it to a float on the fly.

#include <iomanip>
#include <ios>
#include <iostream>
#include <iterator>
#include <list>
#include <fstream>

struct Student {
    std::string name;
    std::string course;
    std::string grade;
    float mark;
};

int main() {

    Student students [6];
    std::string filename = "data.txt";
    std::ifstream file(filename);

    int i = 0;
    
    while(getline(file, students[i].name))
    {
        getline(file, students[i].course);

        string mark; // <-- to hold the string
        getline(file, mark);
        students[i].mark = std::stof(mark);
        
        if (students[i].mark > 89.5) {
            students[i].grade = "HD";
        } else {
            students[i].grade = "PASS";
        }
        
        ++i;
    }
    
    return 0;
}
``