如何解决这些 cpp 错误？ [关闭]

Question

使用 2019 年视觉工作室

我收到的错误是：

E0065 - 104 行

E0112 - 133 行

C2601 - 134 行

C2601 - 146 行

我尝试过重新排列代码段，删除或更改其他代码段，并且已经用尽了我能想到的选项。不太确定出了什么问题，感谢您提供任何帮助。如果需要，我也可以提供我遵循的方向的屏幕截图。

// bring in libraries

#include <iostream>
#include <conio.h>
#include <string>
#include <fstream> // read/write to files
#include <ctime> // time(0)
#include <iomanip> // setprecision( )
using namespace std;
    
    // prototypes
    void deposit(double* ptrBalance);
    void withdrawal(double* ptrBalance, float dailyLimit); // overloaded method this version does not take withdrawal amount
    void withdrawal(double* ptrBalance, float dailyLimit, float amount); // overloaded method that takes withdrawal amount

/// Entry point to the application
int main()
{

    // Create constant variables
    const int EXIT_VALUE = 5;
    const float DAILY_LIMIT = 400.0f;
    const string FILENAME = "Account.txt";


    // create loop variable BEFORE the loop
    short choice = 0;

    // Create balance variable
    double balance = 0.0;

    // Look for the starting balance; otherwise generate a random starting balance
    ifstream iFile(FILENAME.c_str());
    if(iFile.is_open())
    {
        // Did the file open? If so, read the balance.
        iFile >> balance;
        iFile.close();
    }
    else
    {

        // If the file did not open or does not exist, create a random number for the starting balance
        srand(time(0));
        const int MIN = 1000;
        const int MAX = 10000;
        balance = rand() % (MAX - MIN + 1) + MIN;
    }

    std::cout << fixed << setprecision(2) << "Starting Balance: $" << balance << endl;

    // Let's create a pointer and set it to the balance variable location
    double* ptrBalance = &balance; // & means "address of"

        // start the application loop
    do
    {

        // show the menu
        system("cls"); // clears the console screen -- for MAC, use system("clear");
        std::cout << "Menu\n" << endl;
        std::cout << "1) Deposit " << endl;
        std::cout << "2) Withdrawal" << endl;
        std::cout << "3) Check Balance" << endl;
        std::cout << "4) Quick $40" << endl;
        std::cout << "5) Exit" << endl;

        // get user input
        std::cout << "\nEnter your choice: ";
        cin >> choice;

        // run code based on user input
        switch (choice)
        {
        case 1:
            deposit(ptrBalance); // Passing a pointer so only 4 bytes have to cross the system bus
            break;
        case 2:
            withdrawal(ptrBalance, DAILY_LIMIT);
            break;
        case 3:
            std::cout << "Showing current balance..." << endl;
            break;
        case 4:
            std::cout << "Getting quick $40..." << endl;
            break;
        case 5:
            std::cout << "\nGoodbye" << endl;
            break;
        default:
            std::cout << "\nError. Please select from the menu." << endl;
            break;
        }


        /// Make a deposit
        void deposit(double* ptrBalance)
        {
            // get deposit and validate it
            float deposit = 0.0f;

            do
            {
                std::cout << "\nEnter deposit amount";
                cin >> deposit;

                if (cin.fail()) // did they give us a character instead of a number?
                {
                    cin.clear(); // clears fail state
                    cin.ignore(INT16_MAX, '\n'); // clears keyboard buffer
                    std::cout << "\nError. Please input numbers only.\n" << endl;
                    deposit = -1; // set deposit to a "bad" number
                    continue; // restart the loop
                }
                else if (deposit < 0.0f) // check for negative number
                    std::cout << "\nError. Invalid deposit amount.\n" << endl;
            } while (deposit < 0.0f);

            // How do we get the double value located at the pointer?
            // Dereference it using an asterisk
            *ptrBalance += deposit; // same as: *ptrBalance = ptrBalance + deposit;

            std::cout << fixed << setprecision(2) << "\nCurrent ptrBalance: $" << *ptrBalance << endl; // notice asterisk
        }

        /// Make a withdrawal
        void withdrawal(double* ptrBalance, float dailyLimit)
        {
            // get the withdrawal (you should validate this input
            float amount = 0.0f;
            std::cout << "\nEnter withdrawal amount: ";
            cin >> amount;

            // call the overloaded method version that takes the balance, dailyLimit, and withdrawal amount
            withdrawal(ptrBalance, dailyLimit, amount);
        }

        /// Make a withdrawal - this overload accepts balance, dailyLimit, and withdrawal amount
        void withdrawal(double* ptrBalance, float dailyLimit, float amount)
        {
            // take money away from account and show the balance
            if (amount > dailyLimit)
            {
                cout << "\nError. Amount exceeds daily limit." << endl;
            }
            else if (amount > * ptrBalance) // notice the asterisk to dereference the pointer!
            {
                cout << "\nError. Insufficient funds." << endl;
            }
            else
            {
                *ptrBalance -= amount; // same as: *ptrBalance = *ptrBalance - amount;
                cout << "\nHere is your cash: $" << amount << endl;
            }
        }
            cout << fixed << setprecision(2) << "\nCurrent ptrBalance: $" << *ptrBalance << endl;
        

        // pause
        std::cout << "\nPress any key to continue...";
        _getch();
    
    while (choice != EXIT_VALUE);
    return 0;
    // now that the application has ended, write the new balance to the file
    ofstream oFile(FILENAME.c_str());
    oFile << balance << endl;
    oFile.close();

    return 0;
    
    // pause before we clear the screen
    std::cout << "n\Press any key to continue...";
        _getch();

}

Answer 1

C++ 不允许您在另一个函数中定义一个函数。这样做的唯一方法是使用lambdas。所以在定义一个函数时，不要在另一个函数中定义它，而是在其他地方定义它。还有一些其他错误（和警告），我已经更正并注释掉了。

// bring in libraries

#include <iostream>
#include <conio.h>
#include <string>
#include <fstream> // read/write to files
#include <ctime> // time(0)
#include <iomanip> // setprecision( )
using namespace std;

// prototypes   <-- You dont need these.
//void deposit(double* ptrBalance);
//void withdrawal(double* ptrBalance, float dailyLimit); // overloaded method this version does not take withdrawal amount
//void withdrawal(double* ptrBalance, float dailyLimit, float amount); // overloaded method that takes withdrawal amount

/// Make a deposit
void deposit(double* ptrBalance)
{
    // get deposit and validate it
    float deposit = 0.0f;

    do
    {
        std::cout << "\nEnter deposit amount";
        cin >> deposit;

        if (cin.fail()) // did they give us a character instead of a number?
        {
            cin.clear(); // clears fail state
            cin.ignore(INT16_MAX, '\n'); // clears keyboard buffer
            std::cout << "\nError. Please input numbers only.\n" << endl;
            deposit = -1; // set deposit to a "bad" number
            continue; // restart the loop
        }
        else if (deposit < 0.0f) // check for negative number
            std::cout << "\nError. Invalid deposit amount.\n" << endl;
    } while (deposit < 0.0f);

    // How do we get the double value located at the pointer?
    // Dereference it using an asterisk
    *ptrBalance += deposit; // same as: *ptrBalance = ptrBalance + deposit;

    std::cout << fixed << setprecision(2) << "\nCurrent ptrBalance: $" << *ptrBalance << endl; // notice asterisk
}

/// Make a withdrawal - this overload accepts balance, dailyLimit, and withdrawal amount
void withdrawal(double* ptrBalance, float dailyLimit, float amount) // Place this before the other overload as its used by the other one.
{
    // take money away from account and show the balance
    if (amount > dailyLimit)
    {
        cout << "\nError. Amount exceeds daily limit." << endl;
    }
    else if (amount > *ptrBalance) // notice the asterisk to dereference the pointer!
    {
        cout << "\nError. Insufficient funds." << endl;
    }
    else
    {
        *ptrBalance -= amount; // same as: *ptrBalance = *ptrBalance - amount;
        cout << "\nHere is your cash: $" << amount << endl;
    }
}

/// Make a withdrawal
void withdrawal(double* ptrBalance, float dailyLimit)
{
    // get the withdrawal (you should validate this input
    float amount = 0.0f;
    std::cout << "\nEnter withdrawal amount: ";
    cin >> amount;

    // call the overloaded method version that takes the balance, dailyLimit, and withdrawal amount
    withdrawal(ptrBalance, dailyLimit, amount);
}

/// Entry point to the application
int main()
{

    // Create constant variables
    const int EXIT_VALUE = 5;
    const float DAILY_LIMIT = 400.0f;
    const string FILENAME = "Account.txt";


    // create loop variable BEFORE the loop
    short choice = 0;

    // Create balance variable
    double balance = 0.0;

    // Look for the starting balance; otherwise generate a random starting balance
    ifstream iFile(FILENAME.c_str());
    if (iFile.is_open())
    {
        // Did the file open? If so, read the balance.
        iFile >> balance;
        iFile.close();
    }
    else
    {

        // If the file did not open or does not exist, create a random number for the starting balance
        srand(static_cast<unsigned int>(time(0)));  // Cast it to unsigned int.
        const int MIN = 1000;
        const int MAX = 10000;
        balance = static_cast<double>(rand() % (MAX - MIN + 1) + MIN);
    }

    std::cout << fixed << setprecision(2) << "Starting Balance: $" << balance << endl;

    // Let's create a pointer and set it to the balance variable location
    double* ptrBalance = &balance; // & means "address of"

        // start the application loop
    do
    {

        // show the menu
        system("cls"); // clears the console screen -- for MAC, use system("clear");
        std::cout << "Menu\n" << endl;
        std::cout << "1) Deposit " << endl;
        std::cout << "2) Withdrawal" << endl;
        std::cout << "3) Check Balance" << endl;
        std::cout << "4) Quick $40" << endl;
        std::cout << "5) Exit" << endl;

        // get user input
        std::cout << "\nEnter your choice: ";
        cin >> choice;

        // run code based on user input
        switch (choice)
        {
        case 1:
            deposit(ptrBalance); // Passing a pointer so only 4 bytes have to cross the system bus
            break;
        case 2:
            withdrawal(ptrBalance, DAILY_LIMIT);
            break;
        case 3:
            std::cout << "Showing current balance..." << endl;
            break;
        case 4:
            std::cout << "Getting quick $40..." << endl;
            break;
        case 5:
            std::cout << "\nGoodbye" << endl;
            break;
        default:
            std::cout << "\nError. Please select from the menu." << endl;
            break;
        }


        cout << fixed << setprecision(2) << "\nCurrent ptrBalance: $" << *ptrBalance << endl;


        // pause
        std::cout << "\nPress any key to continue...";
        _getch();

    } while (choice != EXIT_VALUE);

    //return 0; <-- You cannot have multiple returns.

    // now that the application has ended, write the new balance to the file
    ofstream oFile(FILENAME.c_str());
    oFile << balance << endl;
    oFile.close();

    // pause before we clear the screen
    std::cout << "\nPress any key to continue...";  // It should be \n, not n\
    _getch();

    return 0;   // Place the return at the end.
}

Answer 2

在您的代码版本中，您已经在main() 中定义了函数。在C++ 中，这是不允许的，即在另一个函数中定义一个函数。你不能在另一个函数的范围内实现一个函数。

由于main() 也是一个函数，因此您会收到链接器错误。

尝试定义main()之外的函数。在外部定义后，您可以通过main() 调用它们。