Change the modulation mode of "constellation decoder" in real time

[????????]

Hello everyone??

    Merry Christmas to you all??

    I'm sorry to bother you here??I would like to ask if there is any method or suggestion for me to control the modulation mode of "OFDM frame equalizer" module and "constellation decoder" through "QT GUI chooser" or other widgets. I know that they cannot be changed. Because they do not have "callback" function, they will be fixed once the flow graph runs. I try to write "callback" function myself, But my C + + level is really limited. There are some errors here. I don't know how to solve them.

/usr/bin/ld: libgnuradio-digital.so.v3.8.2.0-111-g6aad98a6: undefined reference to `gr::digital::ofdm_frame_equalizer_vcvc::set_equalizer(boost::shared_ptr<gr::digital::ofdm_equalizer_base>)'

/usr/bin/ld: libgnuradio-digital.so.v3.8.2.0-111-g6aad98a6: undefined reference to `typeinfo for gr::digital::ofdm_frame_equalizer_vcvc'

collect2: error: ld returned 1 exit status

make[2]: *** [gr-digital/lib/CMakeFiles/digital_qa_header_buffer.cc.dir/build.make:104??gr-digital/lib/digital_qa_header_buffer.cc] error 1

make[1]: *** [CMakeFiles/Makefile2:8900??gr-digital/lib/CMakeFiles/digital_qa_header_buffer.cc.dir/all] error 2

    I refer to the writing method of callback in other modules, but there are still errors, and I think it is not good to change the source code, which may cause many unknown errors, so I want to know whether there are other ways for me to change the modulation mode at any time? Or is it feasible to add the callback function directly?

    Any suggestion would be appreciated??

Bset Regrads,

linge93