数组C ++的Ofstream文本编写问题

Question

Alright, so my infamous code project I've already had problems with twice has been largely reformatted. Now, it looks like this:

#include <iostream>
#include <string>
#include <fstream>

using namespace std;


struct Course
{
    string name;
    double grade;
    int block;
};

Course enter_course()
{
    Course foo;

    cout << "What is the name of the course you wish to enter?\n";
    cin >> foo.name;
    cout << "What block is " << foo.name << " ?\n";
    cin >> foo.block;
    cout << "What is your current grade as a percent?";
    cin >> foo.grade;

    return foo;
}

void display_courses(Course courseList[10], int courseCount)
{
    for (int i=0; i<courseCount; i++){
        cout << i+1 << "\t" << courseList[i].name 
            << "\t\tBlock: " << courseList[i].block
            << "\tGrade: " << courseList[i].grade << "%" << endl;
    }
}

double get_gpa(Course courseList[10], int courseCount)
{
    double gradePoints;
    double total = 0.0;
    for (int i=0; i<courseCount; i++){
        if (courseList[i].grade < 100){
            gradePoints = 4;
        } 
        if (courseList[i].grade < 90){
            gradePoints = 3;
        }
        if (courseList[i].grade < 80){
            gradePoints = 2;
        }
        if (courseList[i].grade < 70){
            gradePoints = 1;
        }
        if (courseList[i].grade < 90){
            gradePoints = 0;
        }
        total += gradePoints;
    }

    return total*1.0/courseCount;

}

void fileOutput()   
{   
    ofstream outputFile;
    outputFile.open("userGrades.txt");
    outputFile << myCourses[10] << endl;
    outputFile.close();
    cout << "Grades saved to file!" << endl;
}

void display_options()
{
    cout << "1. Exit\n";
    cout << "2. Enter a Course\n"; 
    cout << "3. Display Courses\n";
    cout << "4. Display GPA\n";
    cout << "5. Request a text file output\n";

    cout << "\n\n";
}

int main()
{
    bool exit=0;
    int option;
    int courseCount=0;
    Course myCourses[10]; //nobody should ever take more than 10 courses! 

    while (exit == 0)
    {
        cout << "GradeBook 2.0\n";
        display_options();
        cout << "Enter a command.\n";
        cin >> option;

        switch (option)
        {
            case 1: 
                exit = 1;
                break;
            case 2:
                myCourses[courseCount] = enter_course();
                courseCount++;
                break;
            case 3:
                display_courses(myCourses, courseCount);
                break;
            case 4:
                cout << get_gpa(myCourses, courseCount) << endl;
                break;
            case 5:
                fileOutput();
                break;
        }
    }

    return 0;
}

However, at the fileOutput() function, I am experiencing these errors for the same line of code:

error C2065: 'myCourses' : undeclared identifier IntelliSense: identifier "myCourses" is undefined

The only thing I can make sense of is that I need to declare myCourses elsewhere, but I don't know how.

Anyone think they can fix this? If so, compile the code and see. Also, the get_gpa function doesn't seem to be working right, if you can look at that as well.

Answer 1

You have no ostream operator for your Course class, so you cant call that operator in this line:

   outputFile << myCourses[10] << endl;

You could try deleting that line and putting in:

display_courses(myCourses,courseCount)

But sadly that prints to cout . You thus really need to re-write display_courses to take a ostream& parameter and output to it, rather than cout .

Answer 2

In your fileOutput function do the following:

for (int i = 0; i < courseCount; i++)
 {
     outputFile << myCourses[i].name << " " << myCourses[i].grade << " " << myCourses[i].block << endl;

 }

outputFile.close();

Replace the " " with whatever you want to use to delimit the file contents.

Alternatively you could investigate operator overloading and look at overloading the ofstream operator.