Linker complains about undefined reference on vtable

I have this code in my fileType.h.

class FileType{
    private:
        School* m_school;
        string m_fileFormat;
        const string m_cfgFile;
        const string m_inputFile;

    public:
        FileType(string p_fileFormat, string p_cfgFile, string p_inputFile):
                 m_fileFormat(p_fileFormat), m_cfgFile(p_cfgFile), m_inputFile(p_inputFile) {};
        virtual bool parseInputFile();
        virtual bool writeOutputFile(const School& m_school);
        virtual bool checkFormat(); // TBD -- used to check the format of the input file
        virtual bool checkConstraints(); // TBD -- used to check things like only +ve 12 digit in the ID etc
        virtual ~FileType();
};

class XmlType:public FileType{

    public:
        XmlType(string p_fileFormat, string p_cfgFile, string p_inputFile):
            FileType(p_fileFormat, p_cfgFile, p_inputFile) {};
        virtual bool parseInputFile();
        virtual bool writeOutputFile(const School& m_school);
        virtual bool checkFormat(); // TBD -- used to check the format of the input file
        virtual bool checkConstraints(); // TBD -- used to check things like only +ve 11 digit in the ID etc

};


class CsvType:public FileType{

    public:
        CsvType(string p_fileFormat, string p_cfgFile, string p_inputFile):
            FileType(p_fileFormat, p_cfgFile, p_inputFile) {};
        virtual bool parseInputFile();
        virtual bool writeOutputFile(co开发者_如何学Pythonnst School& m_school);
        virtual bool checkFormat(); // TBD -- used to check the format of the input file
        virtual bool checkConstraints(); // TBD -- used to check things like only +ve 11 digit in the ID etc

};

---

In my main I put in :

#include "fileType.h"

    FileType *inputFilePtr, *outputFilePtr;
    string stringOne, stringTwo, stringThree;
    inputFilePtr = new CsvType(stringOne, stringTwo, stringThree);

---

Now my linker tells me that I does not know about the symbols for constructors:

/cygdrive/c/Users/Owner/AppData/Local/Temp/cclieUAi.o:main.cpp:(.text$_ZN7CsvTypeC1ESsSsSs[CsvType::CsvType(std::basic_string, std::allocator >, std::basic_string, std::allocator >, std::basic_string, std::allocator >)]+0x1bf): undefined reference to vtable for CsvType' /cygdrive/c/Users/Owner/AppData/Local/Temp/cclieUAi.o:main.cpp:(.text$_ZN8FileTypeC2ESsSsSs[FileType::FileType(std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::basic_string<char, std::char_traits<char>, std::allocator<char> >)]+0x3a): undefined reference tovtable for FileType' collect2: ld returned 1 exit status

I tried making a dummy constructor with two ints and doing nothing. That worked, but once I put strings, this fails. Any idea what is wrong?

---

You've defined only the constructors, but you've not defined the virtual functions. Only declaring them is not enough. You've to define them as well, which means, the function should have function-body, containing some statements (though it can be blank as well).

//file.h
class A
{ 
   virtual void f(); //this is called declaration
};

//file.cpp
void A::f() //this is called definition
{
  //this is called function-body.
}

---

you declared the virtual destructor but your subclasses don't have one!

where is virtual ~CsvType() { } and virtual ~XmlType() {}

if this is an abstract base class you might consider setting the functions of FileTypeto purely virtual by virtual bool parseInputFile() = 0; so that you can't construct an object of FileType.

Also after virtual bool parseInputFile() {} you don't require a ;