c++ - 如何在 C++ 中输出特定的代码行

Question

我刚刚自己完成了 C++ 的学习(没有外部帮助，只是通过一些网站教程)，现在我正在做我自己的迷你项目。该项目只是一个注册用户的基本银行账户系统(询问用户他们的帐号、姓名和当前余额)

这是我到目前为止所做的。我创建了一个名为“BankAccount.text”的文本文件，现在它包含以下内容:

欢迎使用您的银行账户

您的帐号:

您的名字:

您的姓氏:

您当前的余额:

您的帐号:1

你的名字:ftest

你的姓氏:ltest

您当前的余额:$10

我的问题是，如何向想要查看其信息的用户输出特定的文本行，例如，要求用户输入其帐号(如上所示，为 1)，然后程序输出四行 (1, ftest, ltest, $10)

这是我的代码(我不会展示整个代码):

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

int accnum; //account number of user
string fname; //first name of user
string lname; //last name of user
double balance; //balance amount of user


void show_record()
{
    cout << "Enter your account number: ";
    cin >> accnum;

    /*
    ifstream bnkacct("BankAccount.text"); //needed to read the bank account information file

    if(!bnkacct) //if we couldn't open the output file for reading
    {
        cerr << "Sorry, we could not open your bank account information. We are sorry for the inconvenience" << endl;
        system("pause"); //needed, or else the program will end right away
        exit(1);
    }
    else
    {
        while (bnkacct)
        {
            string strInput;
            getline(bnkacct, strInput);

            cout << strInput << '\n';
        }
    }
    */
}

int main()
{
    cout << "**Banking account information system**" << '\n';
    cout << "\n";
    cout << "Select one of the options below" << '\n';
    cout << "1: Add record to file" << '\n';
    cout << "2: Show record from file" << '\n';
    cout << "3: Search record from file" << '\n';
    cout << "4: Update record information" << '\n';
    cout << "5: Delete record from file" << '\n';
    cout << "6: Exit options" << '\n';
    cout << "\n";

    int option;
    cout << "Enter an option: ";
    cin >> option;

    cout << "\n";

    switch (option)
    {
    case 1:
        add_record();
        break;
    case 2:
        show_record();
        break;
    default: //else if the user did not enter either of the following options
        cout << "You must enter the following options specified!" << endl;
        break;
    }

    system("pause"); //needed if using Visual Studio, else the program ends immediately after program is run

    return 0;
}

那么我该如何解决这个问题呢？

Answer 1

@David C. Rankin 的想法是对的。我为你整理了一个基本的实现。它几乎没有错误检查、数据验证或任何聪明的东西，所以请记住这里有很大的改进空间。但它有效并且应该给你一些继续下去的东西。

struct AccountDetails
{
    string fname; //first name of user
    string lname; //last name of user
    double balance; //balance amount of user
};

void show_record(std::map<int, AccountDetails> bankRecords, int accountNumber)
{
    auto itr = bankRecords.find(accountNumber);
    AccountDetails detailsToDisplay;
    if (itr != bankRecords.end())
    {
        detailsToDisplay = itr->second;

        cout << "Account number: " << accountNumber << '\n';
        cout << "Your first name: " << detailsToDisplay.fname << '\n';
        cout << "Your last name: " << detailsToDisplay.lname << '\n';
        cout << "Your balance: " << detailsToDisplay.balance << '\n';
    }
    else
    {
        cout <<  "Sorry, we could not open your bank account information. We are sorry for the inconvenience." << endl;
    }
}

std::map<int,AccountDetails> ReadRecords(string fileName)
{   
    std::map<int, AccountDetails> records;
    ifstream bankFile(fileName);
    string accountNumber;
    string firstName;
    string lastName;
    string balance;

    AccountDetails temp;

    if(bankFile.is_open())
    {
        while (!bankFile.eof())
        {
            getline(bankFile, accountNumber);
            getline(bankFile, firstName);
            getline(bankFile, lastName);
            getline(bankFile, balance);

            temp.fname = firstName;
            temp.lname = lastName;
            temp.balance = atof(balance.c_str());

            records.emplace(atof(accountNumber.c_str()),temp);
        }   
    }
    return records;
}

int main()
{
    cout << "**Banking account information system**" << '\n';
    cout << "\n";
    cout << "Select one of the options below" << '\n';
    cout << "1: Add record to file" << '\n';
    cout << "2: Show record from file" << '\n';
    cout << "3: Search record from file" << '\n';
    cout << "4: Update record information" << '\n';
    cout << "5: Delete record from file" << '\n';
    cout << "6: Exit options" << '\n';
    cout << "\n";

    int accountNumber = INT_MAX;
    int option;
    cout << "Enter an option: ";
    cin >> option;
    cout << "\n";

    std::map<int,AccountDetails> bankRecords = ReadRecords("BankAccount.text");

    switch (option)
    {
    case 1:
        break;
    case 2:     
        cout << "Enter your account number: ";
        cin >> accountNumber;
        show_record(bankRecords, accountNumber);
        break;

    default: 
        cout << "You must enter the following options specified!" << endl;
        break;
    }

    system("pause"); 
    return 0;
}