Re: [Discuss-gnuradio] Calling C++ method from Python

Hi Patrick,

the typical problem with C++ blocks is that people add public methods to
their _impl, but forget to declare these same methods in their public
non-impl class.
Have you done the same expand magic with the header in your
include/CMakeLists.txt?

Best regards,
Marcus


On 07/06/2015 04:09 AM, Patrick Sathyanathan wrote:
> Hi,
>
> I have worked my way through the Guided Tutorials on gnuradio.org. I have written OOT blocks in Python and managed to expose some set methods in the block as callbacks. Now I have written an OOT C++ block sweeper_cpp_f and I want to expose a couple of setter methods in my block's class as callbacks that can be invoked from Python. Initially I just defined the methods in my sweeper_cpp_f_impl.cc file and added the following to the matching XML file:
>
> <callback>set_direction($direction)</callback>
> <callback>set_trigger_level($trigger_level)</callback>
>
> This builds fine and I am able to use the block in a GRC flow-graph. But at runtime when one of the above methods is invoked as a result of GUI input I get an error message:
>
> File "/home/wpats/ettus/grc/new_sweep_cpp.py", line 141, in set_variable_chooser_direction
> self.tutorial_sweeper_cpp_f_0.set_direction(self.variable_chooser_direction)
> AttributeError: 'sweeper_cpp_f_sptr' object has no attribute 'set_direction'
>
> I looked at built in module sig_source_X_impl.h.t and sig_source_X_impl.cc.t (this is the analog signal source block) in gr-analog as an example for what I am trying to accomplish. I converted my sources into a similar format and modified the CMakeLists.txt in the .../gr-tutorial/lib directory to add:
>
> ########################################################################
> # Invoke macro to generate various sources and headers
> ########################################################################
> include(GrMiscUtils)
> GR_EXPAND_X_CC_H(tutorial sweeper_cpp_X_impl f)
>
> This again builds fine after I edit the generate_helper.py generated script to find an import module. I assumed that the above would do the necessary magic to generate the wrappers for my callback methods but no such luck. I still get the attribute error when invoking my C++ method.
>
> What is the right way to do this ? Any help/suggestions/pointers would be appreciated. I can't be the first one to try to do this seemingly simple task...
>
> Thanks,
>
> --Patrick
>
>
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