Fix Qt Undefined Reference Error

The error “undefined reference to” usually occurs when the linker cannot find implementations of certain functions or variables. To resolve this issue, you can try the following methods:

1. Make sure the implementation files of the function or variable are included in the project, and that they are correctly compiled into target files during compilation. Check if the file paths and names are correct.
2. If you are using functions or variables from a third-party library, make sure that the library is correctly linked. You can try adding the corresponding library file parameter during compilation.
3. For custom functions or variables, make sure they are declared in the header file and implemented correctly in the implementation file.
4. Check if the compilation options are set correctly, including compiler options and linker options. Ensure that the compiler can properly locate all headers and library files.
5. If none of the above methods solve the issue, you can try deleting the compiled files and recompiling the project. Sometimes, recompiling can help resolve certain linker errors.

If none of the above methods have solved the issue, you can try examining the detailed output information of the compiler to find specific linking error messages, in order to better locate and resolve the problem.