Question

I’m having an issue compiling my code when I’m using inheritance. I’ve tried most of everything but no luck compiling

I first have an abstract or ‘interface’ class

class ImyBase
{
    public:
        ImyBase();
        ImyBase(....);
        virtual ~ImyBase();

        virtual void someFuncs() = 0;
        ....
};

Then I have a class that implements this class.

class myBase : public ImyBase
{
    public:
        myBase();
        myBase(....);
        virtual ~myBase();

        void someFuncs();
        ....
};

Then I have a wrapper class.

class myWrap
{
    public:
        myWrap();
        myWrap(....);
        virtual ~myWrap();

        void someFuncs();
        ....
};

Everything works good in the implementation at this point. But when I try to test the wrapper class, that’s where I get the error LNK2019: unresolved external symbol “public: __thiscall ImyBase::ImyBase(void)” (??0ImyBase@@QAE@XZ) referenced in function “public: __thiscall myBase::myBase(void)” (??0myBase@@QAE@XZ)

int main(int argc, char* argv)
{
    myWrap wr;
}

Any help is appreciated! I know its gotta be a dum mistake somewhere…

Answer 1

You have no implementation for the base constructor. The options are defining the constructors in an implementation file or, if they’re empty, in the class definition itself:

class ImyBase
{
    public:
        ImyBase() {};
        ImyBase(....) {};
        virtual ~ImyBase() {};
};

or mark them as default for C++11:

class ImyBase
{
    public:
        ImyBase() = default;
        ImyBase(....) = default;
        virtual ~ImyBase() = default;
};