链接器错误:对vtable的未定义引用 [英] Linker error: undefined reference to vtable
问题描述
我希望您能为我解决问题，该程序是剧院预订程序.
I'm hoping that you can help me with my problem, this program is a theater reservation program.
main.cpp
{
#include <cstdlib>
#include <iostream>
#include "headerMachine.h"
using namespace std;
int main(int argc, char *argv[])
{
Machine machineCall;
Movies moviesCall;
machineCall.menu();
moviesCall.chooseMovie();
system("pause");
return 0;
}
header.h
#include <string>
#include <iostream>
using namespace std;
class Machine
{
public:
void menu(); //
virtual void reserveSeats();
virtual void availableSeats();
void ticketSales();
private:
int task;
};
class Movies: public Machine
{
public:
void chooseMovie(); //
void setTitle();
void timeSlot();
void receipt();
//Inheritance
void reserveSeats();//
void availableSeats();
protected:
int chosenMovie;
int rowNum;
int seatNum;
int seatsThHo[10][10];
int seatsROG[10][10];
int seatsHoTr[10][10];
};
imp.cpp
#include <cstdlib>
#include <iostream>
#include "headerMachine.h"
using namespace std;
const char RESERVED = '*';
const char VACANT = 'o';
void Machine::menu()
{
cout<<"\n [1]Reserve Seats ";
cout<<"\n [2]Available Seats ";
cout<<"\n [3]View Ticket Sales ";
cout<<"\n [0]Exit ";
cout<<"\n\nChoose task number: ";
cin>>task;
}
void Movies::chooseMovie()
{
cout<<"\n [1]The Hobbit ";
cout<<"\n [2]Rise of the Guardians ";
cout<<"\n [3]Hotel Transylvania ";
cout<<"\n [0]Back ";
cout<<"\n\n From what movie: ";
cin>>chosenMovie;
}
void Movies::reserveSeats()
{
cout<<"\nEnter row #: ";
cin>>rowNum;
cout<<"\nEnter seat#: ";
cin>>seatNum;
for(int i=0; i<10; i++)
{
for(int j=0; j<10; j++)
{
seatsThHo[i][j] = VACANT;
seatsROG[i][j] = VACANT;
seatsHoTr[i][j] = VACANT;
}
}
switch(chosenMovie)
{
case 1:
{
cout<<"\nYou wanted to buy ticket from the movie 'The Hobbit': ";
cout<<"\nYour row # is "<<rowNum<<" and you choosed seat # "<<seatNum;
seatsThHo[rowNum][seatNum] = RESERVED;
}
break;
case 2:
{
cout<<"\nYou wanted to buy ticket from the movie 'Rise Of The Guardians': ";
cout<<"\nYour row # is "<<rowNum<<" and you choosed seat # "<<seatNum;
seatsROG[rowNum][seatNum] = RESERVED;
}
break;
case 3:
{
cout<<"\nYou wanted to buy ticket from the movie 'Hotel Transylvania': ";
cout<<"\nYour row # is "<<rowNum<<" and you choosed seat # "<<seatNum;
seatsHoTr[rowNum][seatNum] = RESERVED;
}
break;
case 0:
break;
}
}
void Movies::availableSeats()
{
switch(chosenMovie)
{
case 1:
{
cout<<"\nAvailable Seats for the movie 'Rise Of The Guardians': ";
for(int x=0; x<10; x++)
{
for(int y=0; y<10; y++)
{
cout<<seatsThHo[x][y]<<" ";
}
}
}
break;
case 2:
{
cout<<"\nAvailable Seats for the movie 'Rise Of The Guardians': ";
for(int x=0; x<10; x++)
{
for(int y=0; y<10; y++)
{
cout<<seatsROG[x][y]<<" ";
}
}
}
break;
case 3:
{
cout<<"\nAvailable Seats for the movie 'Hotel Transylvania': ";
for(int x=0; x<10; x++)
{
for(int y=0; y<10; y++)
{
cout<<seatsHoTr[x][y]<<" ";
}
}
}
break;
case 0:
break;
}
}
错误:
[Linker error] main.o:main.cpp:(.text$_ZN7MachineC2Ev[Machine::Machine()]+0x8): undefined reference to `vtable for Machine'
[Linker error] main.o:main.cpp:(.text$_ZN7MachineC1Ev[Machine::Machine()]+0x8): undefined reference to `vtable for Machine'
collect2: ld returned 1 e xit status
C:\Users\Mary Grace\Desktop\Theater Reservation Program\Makefile.win [Error] [TheaterProject.exe] Error 1 (if this is the only error: please check your library includes)
我真的不知道该怎么办，我已经为这个编工作了大约3个小时.
I really don't know what to do now, I've been working for this prog for about 3 hours.
推荐答案
文件 imp.cpp 只是 header.h 的副本.源文件应在头文件中包含方法的实现.
The file imp.cpp is just a copy of header.h. The source file should contain the implementation of the methods in the header file.
喜欢
void Machine::menu()
{
// Code for this method
}
等等.
您遇到的问题是因为您的类中没有构造或析构函数.包含虚函数的类还必须实现构造函数和(虚)析构函数.不必包含任何内容，可以为空，只需定义即可.
The problems you are having is because you don't have a construct or destructor in your classes. A class containing virtual function must also implement a constructor and a (virtual) destructor. The don't have to contain anything and can be empty, the just have to be defined.
错误消息中有一个提示:
One hint is in the error message:
[Linker error] main.o:main.cpp:(.text$_ZN7MachineC2Ev[Machine::Machine()]+0x8): undefined reference to `vtable for Machine'
Here -------------------------------------------------^^^^^^^^^^^^^^^^
实现构造函数和析构函数，它应该可以工作.
Implement the constructors and destructors and it should work.
由于构造函数和析构函数可以为空，因此我建议您仅将它们添加到头文件中的类定义中:
As the constructors and destructors can be empty, I recommend you just add them to the class definition in the header file:
class Machine
{
public:
Machine() {} // Constructor with empty body
virtual ~Machine() {} // Empty virtual destructor
// Rest of the class...
};
对其他班级也做同样的事情，但是当然要用适当的名字.
Do the same for the other class, but of course with the proper names.
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