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

[Marcus Müller]

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I think it might be more of a C++-inherent thing:
If you declare a method in a class:

class daniele_s_class {
public:
 void my_method(int argument);
};

Then you'll have to either implement that method, or can't instantiate
the class -- which is kind of correct, if you think about it, because
that class is simply incomplete. But it's not too bad, either, because
noone ever should instantiate daniele_s_class, it's just meant to
define the interface. That's why we have the "make", which will return
a new instance of the _impl subclass. So, schematically, the GNU Radio
way of doing this is:

class daniele_s_class {
public:
 virtual void my_method(int argument) = 0; //this tells the compiler
that there is a method that a instantiable subclass *must* implement
 static sptr make();
};

daniele_s_class::sptr daniele_s_class::make(){
 return sptr(new daniele_s_class_impl());
}

class daniele_s_class_impl{
 public:
  virtual void my_method(int argument);
};

void daniel_s_class_impl::my_method(int argument){
//do whatever here :)
}

Greetings,
Marcus

On 10.10.2014 15:24, Daniele Nicolodi wrote:
> On 10/10/14 14:29, Daniele Nicolodi wrote:
>> I copied the _impl definition, however, I would prefer to do not
>> copy the interface definition, therefore I defined my block as
>> follows:
>> 
>> namespace gr { namespace baz {
>> 
>> class BAZ_API pll_carriertracking_cc : public
>> gr::analog::pll_carriertracking_cc { public: typedef
>> boost::shared_ptr<pll_carriertracking_cc> sptr; static sptr
>> make(float loop_bw, float max_freq, float min_freq); };
>> 
>> } // namespace baz } // namespace gr
>> 
>> Then I copied the definition of the pll_carriertracking_cc_impl
>> class implementation into my project and changed it where I
>> wanted.
>> 
>> However, in this way, swig is not happy:
> 
> It seems to be a limitation of SWIG (which I don't know much, so I
> may still be doing something wrong). If I define a virtual method
> in the definition of my block interface, SWIG generates the correct
> C++ code.
> 
> I ended up adding a definition for the work() virtual method to fix
> the issue. Again, not the most elegant thing to do, but it
> works...
> 
> Cheers, Daniele
> 
> 
> _______________________________________________ Discuss-gnuradio
> mailing list address@hidden 
> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
> 
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