C++ 新手 - header 重定义错误、链接错误

Question

我是 C++ 的新手，我正在尝试完成一些大学作业。我正在 Visual Studio 2010 中构建我的 C++ 程序。我已经遍历了代码，但无法弄清楚为什么它不起作用。以下是我项目中的所有代码。抱歉，我不得不全部发布，但我不知道问题出在哪里。

员工.h

#ifndef EMPLOYEE_H
#define EMPLOYEE_H
#include <string>

using namespace std;

class Employee
{
public:
    int empNumber;

    string getName();
    int getId();
    float getBaseSalary();
    virtual string getTitle();
    virtual int getNumTaskCompleted();
    virtual float getGrossSalary();
    virtual float getBonus();
    virtual void setEmployeeDetails();
};
#endif

员工.cpp

#include <string>
#include <iostream>

using namespace std;

class Employee
{
private:
    string name;
    int id;
    float salary;

public:
    string getName()
    {
        return this->name;
    }

    int getId()
    {
        return this->id;
    }

    float getBaseSalary()
    {
        return this->salary;
    }

    void setEmployeeDetails()
    {
        cout << "Enter employee name (no spaces): ";
        cin >> this->name;
        cout << "Enter employee id (numeric): ";
        cin >> this->id;
        cout << "Enter employee salary: ";
        cin >> this->salary;
    }
};

项目管理器.h

#ifndef PROJECT_MANAGER_H
#define PROJECT_MANAGER_H
#include <string>
#include "employee.h"

using namespace std;

class ProjectManager : public Employee
{
public:
    string getTitle();
    int getNumTaskCompleted();
    float getGrossSalary();
    float getBonus();
    void setBonus(float bonus);
    void setEmployeeDetails();
};
#endif

项目管理器.cpp

#include <string>
#include <iostream>
#include "employee.h"

using namespace std;

class ProjectManager : public Employee
{
private:
    int numTaskCompleted;
    float bonus;

public:
    string getTitle()
    {
        return "Manager";
    }

    int getNumTaskCompleted()
    {
        return this->numTaskCompleted;
    }

    float getGrossSalary()
    {
        return this->getBaseSalary() + this->bonus;
    }

    float getBonus()
    {
        return this->bonus;
    }

    void setBonus(float bonus)
    {
        this->bonus = bonus;
    }

    void setEmployeeDetails()
    {
        Employee::setEmployeeDetails();

        cout << "Enter tasks completed (numeric): ";
        cin >> this->numTaskCompleted;

        if (numTaskCompleted >= 5)
            this->setBonus(10000.00f);
    }
};

软件工程师.h

#ifndef SOFTWARE_ENGINEER_H
#define SOFTWARE_ENGINEER_H
#include <string>
#include "employee.h"

using namespace std;

class SoftwareEngineer : public Employee
{
public:
    string getTitle();
    int getNumTaskCompleted();
    float getGrossSalary();
    float getBonus();
    void setBonus(float bonus);
    void setEmployeeDetails();
};
#endif

软件工程师.cpp

#include <string>
#include <iostream>
#include "employee.h"

using namespace std;
class SoftwareEngineer : public Employee
{
private:
    int numTaskCompleted;
    float bonus;

public:
    string getTitle()
    {
        return "Engineer";
    }

    int getNumTaskCompleted()
    {
        return this->numTaskCompleted;
    }

    float getGrossSalary()
    {
        return this->getBaseSalary() + this->bonus;
    }

    float getBonus()
    {
        return this->bonus;
    }

    void setBonus(float bonus)
    {
        this->bonus = bonus;
    }

    void setEmployeeDetails()
    {
        Employee::setEmployeeDetails();

        cout << "Enter tasks completed (numeric): ";
        cin >> this->numTaskCompleted;

        if (numTaskCompleted >= 30)
            this->setBonus(5000.00f);
    }
};

程序.cpp

#include <string>
#include <iostream>
#include <iomanip>

#include "employee.h"
#include "projectManager.h"
#include "softwareEngineer.h"

using namespace std;

Employee *_employees[4];

int main()
{
    for (int employeeIndex = 0; employeeIndex < 4; employeeIndex++)
    {
        Employee *CurrentEmployee = new Employee();
        CurrentEmployee->setEmployeeDetails();
        _employees[employeeIndex] = CurrentEmployee;
    }

    cout
        << setw(12) << "Employee" 
        << setw(5) << "Id"
        << setw(15) << "Employee"
        << setw(7) << "Task" 
        << setw(10) << "Base"
        << setw(13) << "Bonus"
        << setw(12) << "Gross" << endl;


    cout
        << setw(11) << "Title" 
        << setw(9) << "Number" 
        << setw(10) << "Name"
        << setw(12) << "Completed"
        << setw(8) << "Salary" 
        << setw(15) << "Entitlement"
        << setw(9) << "Salary" << endl;

    for (int employeeIndex = 0; employeeIndex < 4; employeeIndex++)
    {
        cout
            << setw(12) << _employees[employeeIndex]->getTitle()
            << setw(8)  << _employees[employeeIndex]->getId()
            << setw(13) << _employees[employeeIndex]->getName()  
            << setw(5)  << _employees[employeeIndex]->getNumTaskCompleted()
            << setw(13) << _employees[employeeIndex]->getBaseSalary()
            << setw(14) << _employees[employeeIndex]->getBonus()
            << setw(11) << _employees[employeeIndex]->getGrossSalary() << endl;
    }

    return 0;
}

当我尝试调试这个程序时，我收到一条消息，指出存在构建错误。这些是我遇到的构建错误。

Error 1 error LNK2019: unresolved external symbol "public: int __thiscall Employee::getId(void)" (?getId@Employee@@QAEHXZ) referenced in function _main E:\C++ Assignments\assignment_7\assignment_7\program.obj assignment_7 Error 3 error LNK2019: unresolved external symbol "public: float __thiscall Employee::getBaseSalary(void)" (?getBaseSalary@Employee@@QAEMXZ) referenced in function _main E:\C++ Assignments\assignment_7\assignment_7\program.obj assignment_7 Error 2 error LNK2019: unresolved external symbol "public: class std::basic_string,class std::allocator > __thiscall Employee::getName(void)" (?getName@Employee@@QAE?AV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@XZ) referenced in function _main E:\C++ Assignments\assignment_7\assignment_7\program.obj assignment_7 Error 8 error LNK2001: unresolved external symbol "public: virtual void __thiscall Employee::setEmployeeDetails(void)" (?setEmployeeDetails@Employee@@UAEXXZ) E:\C++ Assignments\assignment_7\assignment_7\program.obj assignment_7 Error 5 error LNK2001: unresolved external symbol "public: virtual int __thiscall Employee::getNumTaskCompleted(void)" (?getNumTaskCompleted@Employee@@UAEHXZ) E:\C++ Assignments\assignment_7\assignment_7\program.obj assignment_7 Error 6 error LNK2001: unresolved external symbol "public: virtual float __thiscall Employee::getGrossSalary(void)" (?getGrossSalary@Employee@@UAEMXZ) E:\C++ Assignments\assignment_7\assignment_7\program.obj assignment_7 Error 7 error LNK2001: unresolved external symbol "public: virtual float __thiscall Employee::getBonus(void)" (?getBonus@Employee@@UAEMXZ) E:\C++

我完全不知道这些错误是什么意思。我查看了错误代码，但无法从中找到任何有助于我了解我做错了什么的信息。

谁能找出问题所在？谢谢!

Answer 1

这些是链接器错误...在编译器完成将您的 C++ 代码编译成目标文件后，链接器然后将这些文件“链接”在一起成为可执行文件。链接器虽然说它找不到要链接在一起的函数，这些函数正在您的 main 函数中调用。

我现在看到的一个大问题是，您已经在头文件中声明了您的类，但随后又在 .cpp 文件中重新声明了它们。那会引起问题。在您的头文件中声明您的类(正如您所做的那样)，但在您的 .cpp 文件中定义您的类函数(您在您的文件中重新声明) .cpp 文件以及定义)。