在C++中使用文件处理的ATM

在C++中使用文件处理可以为ATM机的数据存储和读取提供很好的解决方案。这种方法不仅能够提高程序的可读性和可维护性，还能实现数据的长期保存，使得ATM机可以随时访问以前的交易记录。

文件处理

在C++中，可以用fstream头文件中的类实现对文件的读写操作。该类具有open()和close()成员函数，可以打开和关闭文件。open()函数需要传入文件名和打开方式，打开方式可以是输入、输出或输入输出等。下面是一个例子：

#include <fstream>
using namespace std;

int main() {
    fstream file;
    file.open("file.txt", ios::in | ios::out | ios::app);

    // some code

    file.close();
    return 0;
}

ATM程序

下面是一个使用了文件处理的ATM程序样例，使用了account类表示用户账户，transaction类表示交易记录，ATM类表示ATM机。其中，ATM类中利用了文件处理来读取和写入用户信息和交易记录。

account类

下面是account类的头文件和实现：

// account.h
#ifndef ACCOUNT_H
#define ACCOUNT_H
#include <string>
class account {
public:
    account(const std::string& username, const std::string& password, double balance);
    std::string getUsername() const;
    std::string getPassword() const;
    double getBalance() const;
    void changePassword(const std::string& newPassword);
    void changeBalance(double amount);
private:
    std::string username_;
    std::string password_;
    double balance_;
};
#endif

// account.cpp
#include "account.h"
using namespace std;
account::account(const string& username, const string& password, double balance)
    : username_(username), password_(password), balance_(balance) {}
string account::getUsername() const { return username_; }
string account::getPassword() const { return password_; }
double account::getBalance() const { return balance_; }
void account::changePassword(const string& newPassword) { password_ = newPassword; }
void account::changeBalance(double amount) { balance_ += amount; }

transaction类

下面是transaction类的头文件和实现：

// transaction.h
#ifndef TRANSACTION_H
#define TRANSACTION_H
#include <string>
class transaction {
public:
    transaction(const std::string& username, double amount, const std::string& type);
    std::string getUsername() const;
    double getAmount() const;
    std::string getType() const;
private:
    std::string username_;
    double amount_;
    std::string type_;
};
#endif

// transaction.cpp
#include "transaction.h"
using namespace std;
transaction::transaction(const string& username, double amount, const string& type)
    : username_(username), amount_(amount), type_(type) {}
string transaction::getUsername() const { return username_; }
double transaction::getAmount() const { return amount_; }
string transaction::getType() const { return type_; }

ATM类

下面是ATM类的头文件和实现：

// atm.h
#ifndef ATM_H
#define ATM_H
#include "account.h"
#include "transaction.h"
#include <string>
#include <vector>
class ATM {
public:
    ATM();
    bool login(const std::string& username, const std::string& password);
    void logout();
    double checkBalance() const;
    void deposit(double amount);
    void withdraw(double amount);
private:
    std::vector<account> accounts_;
    std::vector<transaction> transactions_;
    int currentUser_;
    bool loggedIn_;
    void readData();
    void writeData() const;
};
#endif

// atm.cpp
#include "atm.h"
#include <iostream>
#include <iomanip>
#include <fstream>
using namespace std;
ATM::ATM() : accounts_(), transactions_(), currentUser_(-1), loggedIn_(false) {
    readData();
}
bool ATM::login(const string& username, const string& password) {
    for (size_t i = 0; i < accounts_.size(); ++i) {
        if (accounts_[i].getUsername() == username && accounts_[i].getPassword() == password) {
            currentUser_ = i;
            loggedIn_ = true;
            transactions_.emplace_back(username, 0, "Log in");
            return true;
        }
    }
    return false;
}
void ATM::logout() {
    currentUser_ = -1;
    loggedIn_ = false;
    transactions_.emplace_back(accounts_[currentUser_].getUsername(), 0, "Log out");
}
double ATM::checkBalance() const {
    if (loggedIn_) {
        return accounts_[currentUser_].getBalance();
    }
    else {
        return 0.0;
    }
}
void ATM::deposit(double amount) {
    if (loggedIn_) {
        accounts_[currentUser_].changeBalance(amount);
        transactions_.emplace_back(accounts_[currentUser_].getUsername(), amount, "Deposit");
        writeData();
    }
}
void ATM::withdraw(double amount) {
    if (loggedIn_ && amount <= accounts_[currentUser_].getBalance()) {
        accounts_[currentUser_].changeBalance(-amount);
        transactions_.emplace_back(accounts_[currentUser_].getUsername(), -amount, "Withdraw");
        writeData();
    }
}
void ATM::readData() {
    ifstream accountFile("accounts.dat");
    if (!accountFile) {
        cerr << "Could not open account file" << endl;
        exit(EXIT_FAILURE);
    }
    string username, password;
    double balance;
    while (accountFile >> username >> password >> balance) {
        accounts_.emplace_back(username, password, balance);
    }
    accountFile.close();

    ifstream transactionFile("transactions.dat");
    if (!transactionFile) {
        cerr << "Could not open transaction file" << endl;
        exit(EXIT_FAILURE);
    }
    string type;
    while (transactionFile >> username >> balance >> type) {
        transactions_.emplace_back(username, balance, type);
    }
    transactionFile.close();
}
void ATM::writeData() const {
    ofstream accountFile("accounts.dat");
    if (!accountFile) {
        cerr << "Could not open account file" << endl;
        exit(EXIT_FAILURE);
    }
    for (size_t i = 0; i < accounts_.size(); ++i) {
        accountFile << accounts_[i].getUsername() << ' ' << accounts_[i].getPassword() << ' '
            << fixed << setprecision(2) << accounts_[i].getBalance() << endl;
    }
    accountFile.close();

    ofstream transactionFile("transactions.dat");
    if (!transactionFile) {
        cerr << "Could not open transaction file" << endl;
        exit(EXIT_FAILURE);
    }
    for (size_t i = 0; i < transactions_.size(); ++i) {
        transactionFile << transactions_[i].getUsername() << ' ' << fixed << setprecision(2)
            << transactions_[i].getAmount() << ' ' << transactions_[i].getType() << endl;
    }
    transactionFile.close();
}

主程序

下面是主程序的内容：

#include "atm.h"
#include <iostream>
using namespace std;
int main() {
    ATM atm;
    string username, password;
    double amount;
    int choice;
    bool done = false;
    do {
        cout << "1. Login\n2. Check balance\n3. Deposit\n4. Withdraw\n5. Logout\n6. Exit\nYour choice: ";
        cin >> choice;
        switch (choice) {
        case 1:
            cout << "Username: ";
            cin >> username;
            cout << "Password: ";
            cin >> password;
            if (atm.login(username, password)) {
                cout << "Login successful." << endl;
            }
            else {
                cout << "Login failed." << endl;
            }
            break;
        case 2:
            if (atm.checkBalance() > 0) {
                cout << "Your balance is: " << atm.checkBalance() << endl;
            }
            else {
                cout << "Please log in first." << endl;
            }
            break;
        case 3:
            if (atm.checkBalance() > 0) {
                cout << "Amount to deposit: ";
                cin >> amount;
                atm.deposit(amount);
                cout << "Deposit successful." << endl;
            }
            else {
                cout << "Please log in first." << endl;
            }
            break;
        case 4:
            if (atm.checkBalance() > 0) {
                cout << "Amount to withdraw: ";
                cin >> amount;
                atm.withdraw(amount);
                cout << "Withdrawal successful." << endl;
            }
            else {
                cout << "Please log in first." << endl;
            }
            break;
        case 5:
            atm.logout();
            cout << "Logout successful." << endl;
            break;
        case 6:
            done = true;
            break;
        default:
            cout << "Invalid choice." << endl;
            break;
        }
    } while (!done);
    return 0;
}

总结

使用文件处理可以为C++程序提供数据存储和读取的解决方案。在ATM程序中，我们可以将用户信息和交易记录保存在文件中，实现交易记录的长期保存和随时访问。