使用面向对象C++写一份校园卡管理系统，要求文件输入输出，并定义对象，用对象调用操作函数

好的，以下是一份基本的校园卡管理系统的代码：

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

using namespace std;

// 定义学生类
class Student {
private:
    string name;    // 姓名
    int id;         // 学号
    float balance;  // 余额

public:
    Student(string name, int id, float balance) {    // 构造函数
        this->name = name;
        this->id = id;
        this->balance = balance;
    }

    void deposit(float amount) {    // 充值
        balance += amount;
        cout << "充值成功！当前余额为：" << balance << endl;
    }

    void consume(float amount) {    // 消费
        if (balance >= amount) {
            balance -= amount;
            cout << "消费成功！当前余额为：" << balance << endl;
        } else {
            cout << "余额不足，无法完成消费！" << endl;
        }
    }

    void printInfo() {    // 输出学生信息
        cout << "姓名：" << name << endl;
        cout << "学号：" << id << endl;
        cout << "余额：" << balance << endl;
    }

    void writeToFile(ofstream& out) {    // 将学生信息写入文件
        out << name << endl;
        out << id << endl;
        out << balance << endl;
    }
};

// 添加学生
void addStudent(ofstream& out) {
    string name;
    int id;
    float balance;

    cout << "请输入学生姓名：" << endl;
    cin >> name;
    cout << "请输入学生学号：" << endl;
    cin >> id;
    cout << "请输入学生初始余额：" << endl;
    cin >> balance;

    Student student(name, id, balance);
    student.writeToFile(out);
    cout << "添加成功！" << endl;
}

// 查询学生信息
void queryStudent(ifstream& in) {
    int id;
    cout << "请输入要查询的学生学号：" << endl;
    cin >> id;

    string name;
    float balance;

    bool found = false;
    while (in >> name >> id >> balance) {
        if (id == id) {
            found = true;
            cout << "学生信息如下：" << endl;
            cout << "姓名：" << name << endl;
            cout << "学号：" << id << endl;
            cout << "余额：" << balance << endl;
            break;
        }
    }

    if (!found) {
        cout << "未找到该学生信息！" << endl;
    }
}

// 充值
void deposit(ifstream& in, ofstream& out) {
    int id;
    float amount;
    cout << "请输入要充值的学生学号：" << endl;
    cin >> id;
    cout << "请输入充值金额：" << endl;
    cin >> amount;

    string name;
    float balance;
    bool found = false;

    while (in >> name >> id >> balance) {
        if (id == id) {
            found = true;
            Student student(name, id, balance);
            student.deposit(amount);
            student.writeToFile(out);
            break;
        }
    }

    if (!found) {
        cout << "未找到该学生信息！" << endl;
    }
}

// 消费
void consume(ifstream& in, ofstream& out) {
    int id;
    float amount;
    cout << "请输入要消费的学生学号：" << endl;
    cin >> id;
    cout << "请输入消费金额：" << endl;
    cin >> amount;

    string name;
    float balance;
    bool found = false;

    while (in >> name >> id >> balance) {
        if (id == id) {
            found = true;
            Student student(name, id, balance);
            student.consume(amount);
            student.writeToFile(out);
            break;
        }
    }

    if (!found) {
        cout << "未找到该学生信息！" << endl;
    }
}

int main() {
    ofstream out("students.txt", ios::app);    // 打开文件，追加写入
    out.close();

    ifstream in("students.txt");    // 打开文件，读取
    if (!in) {
        cout << "文件打开失败！" << endl;
        return 0;
    }

    int choice;

    while (true) {
        cout << "请选择操作：" << endl;
        cout << "1. 添加学生" << endl;
        cout << "2. 查询学生信息" << endl;
        cout << "3. 充值" << endl;
        cout << "4. 消费" << endl;
        cout << "5. 退出" << endl;
        cin >> choice;

        if (choice == 1) {
            addStudent(out);
        } else if (choice == 2) {
            queryStudent(in);
        } else if (choice == 3) {
            deposit(in, out);
        } else if (choice == 4) {
            consume(in, out);
        } else if (choice == 5) {
            break;
        } else {
            cout << "无效选择！" << endl;
        }
    }

    in.close();    // 关闭文件
    out.close();

    return 0;
}

该程序使用了面向对象的编程方式，将学生信息封装在了一个类中，通过创建对象来调用操作函数。同时，也使用了文件输入输出来保存学生信息，可以方便地进行管理和查询。