c++ - 如何修复 C++ 中的 'arrStud was not declared in this scope' 错误

Question

我目前正在编写一个程序，它将在 4 列(ID、名字、姓氏和 GPA)中显示学生记录，按升序对他们的记录进行排序，并将他们的每个 GPA 重置为 0.0 从排序后的学生记录。

学生记录存储在我称为“StudentInfo.txt”的文本文件中

123456789   John    Johnson    3.5
512434990   Mary    Jackson    3.9
342432444   Peter   Young      2.3
470068625   Jim     Lee        2.9
234324324   Tammy   Gaddis     3.1
121219000   Ester   Schwab     2.7

我遇到的问题是在 ifstream inputFile 之前声明一个结构数组。在第 42、53 和 68 行中显示 “arrStud was not declared in this scope” 的错误消息。

我已经尝试实现 studentInfo **arrStud[SIZE] 和 studentInfo *arrStud[SIZE] 但它没有用，并且出现了另一堆错误。

如果有人能帮我解决这个问题，我将不胜感激!

我当前的代码:

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

using namespace std;

struct studentInfo
{
    int ID;
    string firstName;
    string lastName;
    double GPA;
};

const int SIZE = 100;
void display(/*parameter*/,int);
void resetGPA(studentInfo **, int);
void sortStud(studentInfo **, int);

int main()
{
    int counter = 0;
    int ID;
    string firstName;
    string lastName;
    double GPA;

    // Declare arrStud here...

    ifstream inputFile;

    inputFile.open("StudentInfo.txt");
    if (inputFile.is_open())
    {
        cout << "ID:" << setw(15) << "Name:" << setw(14) << "GPA:" << endl;
        cout << "-------------------------------------------" << endl;

        while(!inputFile.eof())
        {
            inputFile >> ID >> firstName >> lastName >> GPA;
            arrStud[counter] = new studentInfo;

            arrStud[counter]->ID = ID;
            arrStud[counter]->firstName = firstName;
            arrStud[counter]->lastName = lastName;
            arrStud[counter]->GPA = GPA;

            counter++;
        }

        for (int i = 0; i < counter; i++)
        cout << i << arrStud[i]->ID
             << setw(8) << arrStud[i]->firstName
             << setw(10) << arrStud[i]->lastName
             << setw(8) << arrStud[i]->GPA
             << endl;
        cout << "-------------------------------------------" << endl;
        cout << endl;

        inputFile.close();
    }
    else
        cout << "File cannot be opened.";
        inputFile.close();


    display(arrStud, counter);
    cout << endl;
    cout << "Sorting Students by ID..." << endl;
    cout << endl;
    sortStud(arrStud, ID);
    cout << endl;
    cout << "Resetting GPA Data..." << endl;
    cout << endl;
    resetGPA(arrStud, GPA);
}

void display()
{

}

void resetGPA(studentInfo** students, int numStu)
{

    for (int i = 0; i < numStu; i++)
    {
        students[i]->GPA = 0.0;
    }

}

void sortStud(studentInfo** students, int numStu)
{
    int lowestIDIndex; //holds the index in the array students of the student with the lowest ID

    for (int i = 0; i < numStu; i ++)
    {
        lowestIDIndex = i; //always start with lowest ID being first student

        for (int j = i; j < numStu; j++) //j is equal to i so that you don't search the already sorted elements, which are less than i
        {
            if (students[j]->ID < students[lowestIDIndex]->ID) //search for the lowest ID
            {
                lowestIDIndex = j; //keep track of the lowest ID
            }
        }
            //switch the lowest element with the front-most element
            studentInfo* tempStuPtr = students[i];
            students[i] = students[lowestIDIndex];
            students[lowestIDIndex] = tempStuPtr;
    }
}

预期输出:

ID:          Name:          GPA:
-----------------------------------
123456789    John   Johnson     3.5
512434990    Mary   Jackson     3.9
342432444   Peter     Young     2.3
470068625     Jim       Lee     2.9
234324324   Tammy    Gaddis     3.1
121219000   Ester    Schwab     2.7
-----------------------------------


Sorting Students by ID...

ID:          Name:          GPA:
-----------------------------------
512434990    Mary   Jackson     3.9
123456789    John   Johnson     3.5
234324324   Tammy    Gaddis     3.1
470068625     Jim       Lee     2.9
121219000   Ester    Schwab     2.7
342432444   Peter     Young     2.3
-----------------------------------


Resetting GPA Data...

ID:          Name:          GPA:
-----------------------------------
512434990    Mary   Jackson     0.0
123456789    John   Johnson     0.0
234324324   Tammy    Gaddis     0.0
470068625     Jim       Lee     0.0
121219000   Ester    Schwab     0.0
342432444   Peter     Young     0.0
-----------------------------------

Answer 1

您的代码中没有任何地方声明 arrStud!你需要这样的东西，靠近你的 main() 函数的顶部(或者你可以把它作为一个全局变量，比如紧接在 main 的定义之前):

studentInfo* arrStd[SIZE];

然后，在(或接近)main 的末尾，您需要释放由 new 调用创建的内存:

for (int c = 0; c < counter; ++c) delete arrStud[c];

您还需要更正 display 函数的声明和定义，如下所示:

void display(studentInfo**, int);

void display(studentInfo** students, int numStu)
{
    // Do something here, I guess!
}