不同变量类型的向量编译器错误

Question

我的班级的这项作业的目标是询问用户班级中有多少学生。 使用向量库创建一个字符串向量来保存学生的姓名。 创建一个 double 类型的向量来保存学生的平均成绩。

我有两个编译器错误阻止我的代码运行。第 73 和 83 行。我收到以下错误：

main.cpp: In function ‘void add_student()’: main.cpp:73:11: error: request for member ‘push_back’ in ‘grade’, which is of non-class type ‘double’
73 |     grade.push_back(grade);
   |           ^~~~~~~~~

main.cpp: In function ‘void remove_student()’: main.cpp:83:23: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::vector<std::__cxx11::basic_string<char> >::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
83 |     for (int i = 0; i < students.size(); i++)
   |                     ~~^~~~~~~~~~~~~~~~~**

任何帮助将不胜感激。下面是我的全部代码

#include <iostream>
#include <string>
#include <vector>
#include <iomanip>
using namespace std;
vector<string> students;
vector<double> grade;
void add_student();
void remove_student();
void menu();
void print_summary();

int main()
{
    int numStudent;
    char menuSelection; 

    cout << "Welcome to the Student roaster!" << endl;
    cout << "How many students are in your class?:" << endl;
    cin >> numStudent;
    for (int i = 0; i < numStudent; i++)
    {
        add_student();
    }
    cout << "Thank you for entering class information!" << endl;
    

    //calls menu for the user
    menu();


    while (1)
    {
        cout << "selection:" << endl;
        cin >> menuSelection;
        if (menuSelection == 'a')
        {
            add_student();
        }
        else if (menuSelection == 'r')
        {
            remove_student();
        }
        else if (menuSelection == 'p')
        {
            print_summary();
        }
        else if (menuSelection == 'm')
        {
            menu();
        }
        else if (menuSelection == 'q')
            break;
        else
            cout << "Not a valid selection" << endl;
    }
    return 0;
}
void add_student()
{
    string firstName, lastName;
    double grade;

    //ask for student info
    cout << "Please enter student (Fisrt Last Grade) info: " << endl;
    cin >> firstName >> lastName >> grade;

    firstName += " ";
    firstName += lastName;

    //inserts new student
    students.push_back(firstName); 
    grade.push_back(grade);
}
void remove_student()
{
    string first, last;
    cout << "Enter the student (First Last) to remove :\n";
    cin >> first >> last;
    first += " ";
    first += last;
    int loc = 0;
    for (int i = 0; i < students.size(); i++)
    {
        if (students[i] == first)
        { // finding the location to erase
            loc = i;
            break;
        }
    }
    students.erase(students.begin() + loc); //removing using erase function
    grade.erase(grade.begin() + loc);
}
void menu()
{
    cout << "Please choose one of the following options:\n";
    cout << "a: add a student\n";
    cout << "r: remove a student\n";
    cout << "p: print the class summary\n";
    cout << "m: print menu\n";
    cout << "q: quit program\n";
}
void print_summary()
{
    cout << "class summary" << endl;
    cout << "--------------------------------" << endl;
    cout << "Name" << setw(20) << "Grade" << endl;
    cout << "-------" << setw(20) << "--------" << endl;
    int n = students.size();
    double total = 0;

    //cycles through each student
    for (int i = 0; i < n; i++)
    {
        int temp = students[i].size();
        int loc = 20 - temp;
        cout << students[i] << setw(loc) << grade[i] << endl;
        total += grade[i];
    }
    cout << "Number of students: " << endl;
    cout << "------------------" <<endl;
    cout << n << " " << endl;
    total = (total) / n;
    cout << "Average Grade: " << endl;
    cout << "--------------" << endl;

    //limits the deciaml places to 2
    cout << fixed << setprecision(2) << total << " " << endl;
}

Answer 1

局部变量的名称与全局变量的名称相同。 所以你应该重命名局部变量。

62)  double grade_;
66)  cin >> firstName >> lastName >> grade_;
73)  grade.push_back(grade_);