C++ 派生 class 未正常运行

Question

我是编程新手，我遇到了这个我无法解决的问题。我已经尝试了所有我能想到的。我已经做好了这么简单的错误的准备。

main.cpp

#include <iostream>
#include <iomanip>
#include "new_employee.h"
#include "new_employee.cpp"
#include "permanent_employee.cpp"

using namespace std;

int in_employee[4] = {101, 102, 103, 104};
int in_bankaccount[4] = {80045001, 80045002, 80045003, 80045004};
float in_hours[4] = {40, 50, 50, 51};
float in_rate[4] = {22, 22, 24, 26};

int main()
{
    for(int i=0;i<4;i++)
{
    new_employee employee[i](in_employee[i], in_bankaccount[i]);
}
///permanent_employee employee2(in_employee[1], in_bankaccount[1]);
///permanent_employee employee3(in_employee[2], in_bankaccount[2]);
///permanent_employee employee4(in_employee[3], in_bankaccount[3]);
}

new_employee.h

#if !defined NEW_EMPLOYEE
#define NEW_EMPLOYEE

class new_employee
{
public:
    new_employee();
    new_employee(int employee_number, int account_number);
private:
    int employee_no, account_no;
    float hourly_rate, hours_worked;
};

class permanent_employee : public new_employee
{
public:
    permanent_employee();
    permanent_employee(int employee_number, int account_number);
private:
    float union_deduction, vhi_deduction;
};
#endif

new_employee.cpp

#include <iostream>
#include <iomanip>
#include "new_employee.h"

using namespace std;

new_employee::new_employee()
{
    employee_no = 0;
    account_no = 0;
}

new_employee::new_employee(int employee_number, int account_number)
{
    employee_no = employee_number;
    account_no = account_number;
}

permanent_employee.cpp

#include <iostream>
#include <iomanip>
#include "new_employee.h"

using namespace std;

permanent_employee::permanent_employee()
{
    employee_no = 0;
    account_no = 0;
}

permanent_employee::permanent_employee(int employee_number, int account_number)
{
    employee_no = employee_number;
    account_no = account_number;
}

因此，由于直接从 Codeblocks 复制的以下错误，我什至没有尝试正确运行程序的原始功能。

Z:\C++\Assignment 3 - Payroll Processing\new_employee.h||In constructor 'permanent_employee::permanent_employee()':|

Z:\C++\Assignment 3 - Payroll Processing\new_employee.h|10|error: 'int new_employee::employee_no' is private|

Z:\C++\Assignment 3 - Payroll Processing\permanent_employee.cpp|9|error: within this context|

Z:\C++\Assignment 3 - Payroll Processing\new_employee.h|10|error: 'int new_employee::account_no' is private|

Z:\C++\Assignment 3 - Payroll Processing\permanent_employee.cpp|10|error: within this context|

Z:\C++\Assignment 3 - Payroll Processing\new_employee.h||In constructor 'permanent_employee::permanent_employee(int, int)':|

Z:\C++\Assignment 3 - Payroll Processing\new_employee.h|10|error: 'int new_employee::employee_no' is private|

Z:\C++\Assignment 3 - Payroll Processing\permanent_employee.cpp|15|error: within this context|

Z:\C++\Assignment 3 - Payroll Processing\new_employee.h|10|error: 'int new_employee::account_no' is private|

Z:\C++\Assignment 3 - Payroll Processing\permanent_employee.cpp|16|error: within this context|

Z:\C++\Assignment 3 - Payroll Processing\main.cpp||In function 'int main()':|

Z:\C++\Assignment 3 - Payroll Processing\main.cpp|18|error: variable-sized object 'employee' may not be initialized|

Z:\C++\Assignment 3 - Payroll Processing\main.cpp|18|warning: unused variable 'employee' [-Wunused-variable]| ||=== Build finished: 9 errors, 1 warnings (0 minutes, 0 seconds) ===|

我正在尝试使用派生的 class permanent_employee 创建基础 class new_employee。在我看来，每个人都在尝试访问对方的变量。如果有任何反馈，我将不胜感激。

感谢您的帮助。

PS。我是这个网站的新手，如果我发错了，我很抱歉。

Answer 1

变化：

permanent_employee::permanent_employee(int employee_number, int account_number)
{
    employee_no = employee_number;
    account_no = account_number;
}

要调用基础 class 构造函数：

permanent_employee::permanent_employee(int employee_number, int account_number)
 : new_employee(employee_number, account_number)
{
}

由于 private 为 new_employee 声明了成员变量，即使派生的 classes 也无法访问它们。如果您希望派生的 classes 能够修改它们，您可以将它们声明为 protected（但有时出于不变保存等原因，您不会这么做）。

Answer 2

您的成员变量的可访问性有问题。一般来说，可访问性是这样的：

Public : 任何人都可以看到并改变这些人。受保护：包含这些变量作为成员的 class 和任何派生的 class 都可以更改这些变量。 classes 之外无法访问它们。私有：只有包含这些成员变量的class可以以任何方式更改或使用它们。

错误是由于 permanent_employee class 试图访问 new_employee class 的私有成员造成的。您也可以尝试从派生构造函数调用基础 class 构造函数。

无论你走哪条路，我都强烈建议你在做任何其他事情之前花一些时间来充分理解 public、protected 和 private 成员变量和函数之间的区别。从长远来看，这将使您的生活更加轻松运行。

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