如何解决如何解决这些 cpp 错误？
使用 VISUAL STUDIO 2019
我收到的错误是：
E0065 - 第 104 行
E0112 - 第 133 行
C2601 - 第 134 行
C2601 - 第 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，任何帮助表示赞赏。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,amount);
}
/// Make a withdrawal - this overload accepts balance,and withdrawal amount
void withdrawal(double* ptrBalance,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();
}
解决方法
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，不要在另一个函数内部定义它，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 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,and withdrawal amount
withdrawal(ptrBalance,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.
}
在您的代码版本中，您已经在 main() 中定义了函数。在 C++ 中，不允许这样做，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。
尝试在 main() 之外定义函数。在外部定义后，您可以从 main() 调用它们。
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