c++ - 使用 fstream 将文本文件导入变量？

Question

我正在尝试创建一个简单的程序，它像 ATM 一样用于学习目的。到目前为止，我有一个工作程序，但现在我想“将其提升到一个新的水平”，如果您愿意，并从文本/csv 文件导入我的银行余额，然后分配给一个变量，如果对余额进行任何更改我还想将这些更改写入所述文本文件。到目前为止，我已经在网上进行了搜索，但未能找到很多似乎与我的问题特别相关的信息。

#include <iostream>
#include <iomanip>
#include <string>
#include <fstream>
using namespace std;

//calculates money withdrawal.
int main(){
    double currentBalance = -250.63;
    double prevBalance = currentBalance;
    double withdrawal = 0;
    double deposit = 0;
    double deficit = currentBalance;
    double updatedWithdrawal = 0; //(currentBalance - withdrawal)
    double updatedDeposit = 0; //(currentBalance + deposit)
    string answer = "blah";

    cout << "Welcome to bank bro's banking services.\nWhat would you like to do? Withdrawal, Deposit, or View Account Status(VAS): ";
    cin >> answer; // asks the user if they intend to withdrawal, or deposit.

    if (answer == "VAS"){
        if (currentBalance > 0)
            cout << "\n Your account is in good standing." << endl;
        else{
            cout << "\n You currently owe: $" << deficit << endl;
        }
        cout << "\n Your current balance is: $" << currentBalance << endl;
    }
    else if (answer == "vas"){
        cout << "\n Your current balance is: " << currentBalance << endl;
        if (currentBalance > 0)
            cout << "\nYour account is in good standing." << endl;
        else{
            cout << "You currently owe: $" << deficit << endl;
        }
        cout << "\nYour urrent balance is: $" << currentBalance << endl;
    }
    else if (answer == "Withdrawal"){
        cout << "\nHow much would you like to take out? ";
        cin >> withdrawal;
        if (withdrawal > currentBalance)
            cout << "\nYou don't have sufficient funds." << endl;
        else{
            updatedWithdrawal = (currentBalance - withdrawal);
            cout << "You have $" << updatedWithdrawal << " left, cash is dispensed below." << endl;
            cout << "\n\n\n Thank you, come again!" << endl;
        }
    }
    else if (answer == "withdrawal"){
        cout << "\nHow much would you like to take out? ";
        cin >> withdrawal;
        if (withdrawal > currentBalance)
            cout << "\nYou don't have sufficient funds." << endl;
        else{
            updatedWithdrawal = (currentBalance - withdrawal);
            cout << "\nYou have $" << updatedWithdrawal << " left, cash is dispensed below." << endl;
            cout << "\n\n\n Thank you, come again!" << endl;
        }
    }
    else if (answer == "Deposit"){
        cout << "\nHow much would you like to deposit? ";
        cin >> deposit;
        updatedDeposit = (currentBalance + deposit);
        cout << "\nYour previous balance of $" << prevBalance << " \nhas been updated and $" << deposit << 
            " \nhas been added to your account, bringing the total available balance to $" << updatedDeposit << endl;
        cout << "\n\nThank you come again!" << endl;
   }
    else if (answer == "deposit"){
        cout << "\nHow much would you like to deposit? ";
        cin >> deposit;
        updatedDeposit = (currentBalance + deposit);
        cout << "\nYour previous balance of $" << prevBalance << " \nhas been updated and $" << deposit <<
            " \nhas been added to your account, bringing the total available balance to $" << updatedDeposit << endl;
        cout << "\n\nThank you come again!" << endl;
    }
    else{
        cout << "I don't recognize that command, restart and try again." << endl;
    }
    return 0;
}

非常感谢任何帮助! :)

Answer 1

为了在 C++ 中使用文件，您需要一个 fstream。您应该查看文档 http://en.cppreference.com/w/cpp/io/basic_fstream/basic_fstream哪里正确描述了如何在 C++ 中与文件交互。

您需要一个以写入模式打开的fstream，以便以您选择的格式保存所有数据。之后，您需要以读取模式打开一个 fstream 以便再次从中读取数据。

文件格式由您决定。您可以以任何您想要的格式序列化数据。您需要记住，在序列化过程之后，必须准确读取所有数据的写入方式。