Case Study: Students

Section 15.13 Case Study: Students - Part 3

All that is left is to read in the data from the file. Time to tackle that.

Subsection 15.13.1 Reading the File

The previous exercise had a function getTestStudents() that created a few students we could use to test our code with. To make the program work with the data in the file, we can design a similar function that reads that data and returns a vector of students. Then we can swap the call to getTestStudents() with a call to this new function.

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It might be useful for the function to take the filename to read from as its parameter. That would make it possible to have a smaller test file that we can use for testing a larger file that gets used by the final program.

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We already have functions that will take an entire line of text and create a Name or a Status or a vector of doubles. So all this function has to do is to use getline 3 times for each student. We will assume that we don’t know how many students there are in the file, so we will read until eof.

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Checkpoint 15.13.1.

Construct the algorithm for getStudentData. Make sure to check for failure after trying to read in the next three lines before using them to make a student.

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vector<Student> getStudentData(const string& filename) { #tag:start; depends:;
---
    ifstream file(filename); #tag:if; depends:start;
---
    if (!file.is_open()) {
        throw runtime_error("Could not open file");
    } #tag:ifcheck; depends:if;
---
    vector<Student> students; #tag:vec; depends:start;
---
    while (!file.eof()) { #tag:while; depends:vec,ifcheck;
---
        string nameLine, statusLine, scoresLine;
        getline(file, nameLine); #tag:l1; depends:while;
---
        getline(file, statusLine); #tag:l2; depends:l1;
---
        getline(file, scoresLine); #tag:l3; depends:l2;
---
        if(file.fail()) {
            break; // Exit loop if reading fails
        } #tag:failcheck; depends:l3;
---
        Student student = createStudent(nameLine,
                                        statusLine,
                                        scoresLine); #tag:st; depends:failcheck;
---
        students.push_back(student);
    } #tag:push; depends:st;
---
    return students;
} #tag:end; depends:push;

#include <iostream>
#include <vector>
#include <string>
#include <sstream>
#include <stdexcept>
#include <fstream>
using namespace std;

struct Name {
    string first;
    string middle;
    string last;
};

enum class Status {
    INACTIVE,
    ACTIVE
};

struct Student {
    Name name;
    Status currentStatus;
    vector<double> scores;
};

Name createName(const string& line) {
    Name name;
    stringstream ss(line);
    ss >> name.first;
    ss >> name.middle;
    ss >> name.last;
    return name;
}

Status createStatus(const string& line) {
    if (line == "Active") {
        return Status::ACTIVE;
    }
    else if (line == "Inactive") {
        return Status::INACTIVE;
    }
    else {
        throw logic_error("Invalid status value");
    }
}

vector<double> createScores(string line) {
    vector<double> scores;
    size_t nextComma = line.find(',');
    while (nextComma != string::npos) {
        string scoreStr = line.substr(0, nextComma);
        double score = stod(scoreStr);
        scores.push_back(score);
        line = line.substr(nextComma + 1);
        nextComma = line.find(',');
    }
    // Handle the last score after the last comma
    double score = stod(line);
    scores.push_back(score);
    return scores;
}

Student createStudent(const string& nameLine,
                      const string& statusLine,
                      const string& scoresLine) {
    Student student;
    student.name = createName(nameLine);
    student.currentStatus = createStatus(statusLine);
    student.scores = createScores(scoresLine);
    return student;
}

double calculateAverage(const vector<double>& scores) {
    double total = 0.0;
    for (double score : scores) {
        total += score;
    }
    return total / scores.size();
}
==PARSONSCODE==

int main() {
    vector<Student> studentList = getStudentData("Students.txt");
    cout << "Averages for active students:" << endl;
    for (const Student& s : studentList) {
        // print out just active students
        if (s.currentStatus == Status::ACTIVE) {
            cout << "Name: " << s.name.first << " ";
            cout << calculateAverage(s.scores) << endl;
        }
    }
}

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