Re: [Discuss-gnuradio] Sub-classing a block defined in an _impl class

[Johannes Demel]

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Hi Daniele,

_impl classes are not meant to be subclassed usually.
GR distinguishes between interface or public headers, which are
located in the include directory and private headers which are located
in the lib directory.
You can just add new classes to your lib folder and use them within
this folder. But if you want to export these classes and make them
accessable from Python, you need a public header for it.

On 10.10.2014 12:03, Daniele Nicolodi wrote:
> Hello,
> 
> this question my arise from my ignorance about C++, but I don't 
> understand how, if it is possible, to sub-class a GNURadio block
> that has moat of his code in an _impl class.
> 
> To my understanding I would need to subclass both the class
> defining the block and his _impl class. However, it seems that the
> _impl class is not part of the exposed API, therefore there is no
> way to subclass it. There is way to achieve this without copying
> around significant portions of code?
The public description of a block is in the corresponding include
folder. It is pure virtual to make sure it remains as an interface file.

> The case at hand is subclassing gr::analog::pll_carriertracking_cc 
> changing the phase_detector() method to use the regular atan2()
> instead of the fast version.
You may just change this in GR directly. You have a personal copy of
the code so there is nothing that should contradict this approach.
Unless you want to compare the two but even then you should be able to
accomplish that.

I hope that gives you an idea of the structure and may help you solve
your problem.

Cheers
Johannes
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