如何在不使用 C++ 中的向量的情况下分隔逗号分隔值？

Question

我正在使用 C++ 编写 ATM 机器代码。我知道最好使用二进制文件和类这样每个帐户的文件大小都完全相同，即使它是空的。我正在寻找非常非常简单的东西。

我在解析 .txt 文件中的逗号分隔值时遇到问题。有时我得到值，有时我只得到第一个值。我花了几天时间来找出它的解决方案。我搜索了互联网和计算器，几乎每个答案都使用矢量或其他东西。

我没有使用 strcmp 进行数组比较，而是创建了自己的函数来比较字符。

从代码来看，似乎我已经做了很多，只是需要一点推动。请看看我的代码，让我知道我哪里错了。我要消除语义错误！并修改如下代码，达到预期效果。

#include<iostream>
#include<conio.h>
#include<fstream>
#include<cstring>
#include<string>
#include<sstream>
#include<stdlib.h>

using namespace std;

void checkBalance();
void createAccount();
void deposit();
void withdraw();
void transfer();
void login();
void mainScreen();
void menuScreen();
// For file handling
void saveAccountToFile();
bool checkAccountExists(char*);
void loadAccount(char *);
void loadBeneficiary(char*);

bool compare(char *, char *);

const char * FILE_NAME = "accounts.txt";

char username[50];
char pin[5];
double balance = 0.0;

// Beneficiary Variables

char b_username[50];
char b_pin[5];
double b_balance = 0.0;

void menuScreen()
{
    char opt;
    do {
    system("cls");
    cout << "\n\n\t\t CMD - ATM";
    cout << "\n\n\tMENU";
    cout << "\n\n\t01. Check Balance";
    cout << "\n\n\t02. Withdraw";
    cout << "\n\n\t03. Deposite";
    cout << "\n\n\t04. Transfer to Another account";
    cout << "\n\n\t05. Logout";
    opt = _getch();
    switch (opt)
    {
    case '1':
        checkBalance();
        break;
    case '2':
        withdraw();
        break;
    case '3':
        deposite();
        break;
    case '4':
        transfer();
    case '5':
        cout << "\n\nThanks for using CMD ATM. Press any key to exit...";
        _getch();
        exit(1);
    default:
        cout << "\a\n\nIncorrect input. Press any key to try agian!";
        _getch();
    }
} while (opt != '5');
}

void mainScreen() 
{
char opt;
do {
    system("cls");
    cout << "\n\n\t\t CMD - ATM";
    cout << "\n\n\tMENU";
    cout << "\n\n\t01. Create Account";
    cout << "\n\n\t02. Login";
    cout << "\n\n\t03. Exit";
    opt = _getch();
    switch (opt)
    {
    case '1':
        createAccount();
        break;
    case '2':
        login();
        break;
    case '3':
        exit(1);
    default:
        cout << "\a\n\nIncorrect input. Press any key to try agian!";
        _getch();
    }
} while (opt != '3');
}

void saveAccountToFile() {

ofstream outFile;
outFile.open(FILE_NAME, ios::app);
if (outFile.is_open()) {
        outFile << username << ',' <<
            pin << ',' << balance << "\n";
}
outFile.close();
}

bool checkAccountExists(char * userName)
{   
int i = 0;

char temp[50] = {'0'};
ifstream inFile;
string line;
inFile.open(FILE_NAME);

if (inFile.is_open()) {
    while (getline(inFile, line)) {
        stringstream ss(line);
        string value;
        while (getline(ss, value, ',')) {
            if (i == 0) {
                strcpy(temp,value.c_str());
                if(compare(userName, temp)){
                    cout << "closing";
                    getchar();
                    inFile.close();
                    return true;
                }
                i = 1;
            }
            else if (i == 1) {
                i = 2;
            }
            else if (i == 2) {
                i = 0;
            }       
        }
    }
    inFile.close();
}
return false;
}


void loadAccount(char * userName)
{

int i = 0;
ifstream inFile;
string line;
inFile.open(FILE_NAME);

if (inFile.is_open()) {
    while (getline(inFile, line)) {
        stringstream ss(line);
        string value;
        while (getline(ss, value, ',')) {
            if (i == 0) {
                strcpy(username, value.c_str());
                i = 1;
            }
            else if (i == 1) {
                strcpy(pin, value.c_str());
                i = 2;
            }
            else if (i == 2) {
                balance = atof(value.c_str());
                i = 0;
            }
            if(compare(username,userName))
            {
                inFile.close();
                break;
            }       
        }
    }
    inFile.close();
}
}

void loadBeneficiary(char * userName)
{

int i = 0;
ifstream inFile;
string line;
inFile.open(FILE_NAME);

if (inFile.is_open()) {
    while (getline(inFile, line)) {
        stringstream ss(line);
        string value;
        while (getline(ss, value, ',')) {
            if (i == 0) {
                strcpy(b_username, value.c_str());
                i = 1;
            }
            else if (i == 1) {
                strcpy(b_pin, value.c_str());
                i = 2;
            }
            else if (i == 2) {
                b_balance = atof(value.c_str());
                i = 0;
            }   
            if(strcmp(b_username, userName)){
                inFile.close();
                break;
            }   
        }
    }
    inFile.close();
}
}

void login()
{
char tempName[50];
char tempPin[5];
cout << "\n\nEnter user name: ";
cin.getline(tempName, sizeof(tempName));
if (checkAccountExists(tempName)) {
    cout << "\n\nEnter user pin: ";
    cin.getline(tempPin,sizeof(tempPin));
    loadAccount(tempName);
    if (compare(tempPin, pin)) {
        cout << "\n\nLog in successfull!";
        cout << "\n\nPress any key to continue...";
        _getch();
        menuScreen();
    }else {
        cout << "User name or pin incorrect!";
        _getch();
    }
}
else {
    cout << "\n\nRecord not found. Press any key to continue...";
    _getch();
}

}

void checkBalance()
{
system("cls");
cout << "\n\n\tUser name = " << username;
cout << "\n\n\tBalance = " << balance;
_getch();
}

bool compare(char * msg1, char * msg2){
int count = 0;
int size = sizeof(msg1);
if(sizeof(msg2) == size){
    for(int i = 0; i < size; i++){
        if(msg1[i]==msg2[i]){
            count++;
        }
    }
    if(count == size)
        return true;
}

return false;
}

int main(int argc, char** argv) {

mainScreen();
getchar();
return 0;
}

TXT 文件

jhon,5155,99999.99
bot,4414,232323
theta,2111,34234

Answer 1

关于如何简化阅读循环，比如

while (getline(inFile, line)) {
    stringstream ss(line);
    string value;

    getline(ss, value, ',');
    string name = value;

    getline(ss, value, ',')
    string pin = value;

    getline(ss, value)
    double balance = stod(value);

    // Now use the name, pin and balance some way...
}

因为当你只需要名字时你不需要第二次和第三次 getline 调用，只需要第一次。

还可以考虑使用 structures 来存储名称、密码和余额，然后使用 container (for example a vector) 来存储结构。

另外，为了简单起见，我建议您只阅读文件一次。然后遍历向量以找到您需要的数据。

Answer 2

这是一个不使用 stringstream

的替代方案

while(getline(inFile,line,',')){

        strcpy(username, line.c_str());

        getline(inFile,line,',');
        strcpy(pin, line.c_str());

        getline(inFile,line,'\n');
        balance = atof(line.c_str());

        if(compare(username,userName)){
            inFile.close();
            break;
        }else 
            continue;

    }

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