[Discuss-gnuradio] Custom GRC block not accepting derived class objects

[Perez, Tracie R]

I'm hoping for suggestions from the GRC and swig savvy folks on the list.

I am trying to add LDPC functionality to gr-fec [1]. I made a GRC block for a 
decoder class. The decoder class constructor accepts a base class called 
fec_mtrx. In GRC, I am trying to give the decoder block an input of an object 
of a class derived from fec_mtrx, called ldpc_R_U_mtrx. The issue is that swig 
is giving an error that it expects the base class as the argument.

From the swig documentation, this type of inheritance and type checking seems 
to be fully supported and handled by swig. Is there something else I need to 
consider in either the block's cheetah template for the make call, or the swig 
files?

The organization of the classes is like: 

class FEC_API ldpc_R_U_mtrx : public fec_mtrx  {    };

class FEC_API ldpc_bit_flip_decoder_impl : public ldpc_bit_flip_decoder
{
public:
    ldpc_bit_flip_decoder_impl(fec_mtrx *mtrx_obj, unsigned int max_iter=100);
}

And then in variable_ldpc_bit_flip_decoder.xml I've got: self.$(id) = $(id) = 
fec.ldpc_bit_flip_decoder.make($matrix_object, $max_iterations)

In my flowgraph, I provide the decoder block an input of a ldpc_R_U_mtrx 
variable, and swig throws:
TypeError: in method 'ldpc_bit_flip_decoder_make', argument 1 of type 
'gr::fec::code::fec_mtrx *

So to me, it seems like swig is not recognizing that the ldpc_R_U_mtrx class 
derives from fec_mtrx. Not sure what to do about that except to try and 
“un-inherit" the classes and overload the decoder constructor...

Thanks for any tips,
tracie


[1] github.com/tracierenea/gnuradio/tree/ldpc_mods