c++ - Linkage Error with Inherited Class -

I have a static library and another program to use it.

If I define the headers in the static library, on the other hand if I use a code of conduct with a Qt class, then

< P> Code> class> TCP communication: public QTcpServer

When I compile the code which uses this static library, I get a linking error.

  & gt; MStoDKAPId.lib Tcp Communication.obj): Error LNK2019: Unsolved external symbol "__declspec (dllimport) public: Virtual __thiscall QTcpServer :: ~ QTcpServer (zero)" (__imp _ ?? 1QTcpServer @@ UAE @ Xs) function referred to in the "Public : Virtual __thiscall Tcp Communications:: ~ TCP Communication (Zero) "(? 1Tcp Communication @ @ UAE @ Xs)  

What could be the problem? Thank you.

Applications using your static library QT