Re: Howto override the argument names of certain class member functions

Hi William,

I have a large class library. There are multiple functions that have a, 
say, "(Channel& chan)" argument. In most cases these are used to return 
values, but in some cases the functions modify the contents of the 
object who's reference is passed. So I cannot generically use the 
%template system as that only applies to the type and names of arguments 
passes, there is not ability to say a particular function is just using 
that argument as an output return. A lot of this libraries code is auto 
generated from a IDL and I generate a set of modified *.h files with the 
argument names changed to OUTPUT at the appropriate places but quite a 
few class member functions are not like that.

Terry
On 27/06/2020 10:05, William S Fulton wrote:
> Hi Terry
>
> The %apply that Rui mentioned just applies the typemap you want for 
> these named arguments and types. You can use these %apply directives 
> before SWIG parses your unmodified C++ header files containing the 
> original argument names. I don't see a reason to modify your header 
> files, can you elaborate why you think you need to do that?
>
> William
>
> On Tue, 23 Jun 2020 at 06:19, Terry Barnaby <[email protected] 
> <mailto:[email protected]>> wrote:
>
>     Many thanks for your reply, yes I could do something like that but
>     this
>     is a complex library with lots of classes and functions defined in
>     header files and I wanted to leave those header files alone and
>     get SWIG
>     to use them directly. I don't want to rewrite the header files
>     into SWIG
>     definition files as that would be a lot of work and
>     unmaintainable. So I
>     was hoping that SWIG could, somehow, apply an argument rename on a
>     function by function basis.
>
>     I have done it at the moment by pre-processing all of the header
>     files
>     through sed before SWIG sees them, but that's a bit messy.
>
>     Terry
>     On 22/06/2020 10:54, Rui Oliveira wrote:
>     > Hey,
>     >
>     > You're probably looking to do something like:
>     >
>     > %apply (float complex *OUTPUT) {(liquid_float_complex *_y),
>     > (liquid_float_complex *_x_hat)};
>     > void modem_modulate(modem _q, unsigned int _s,
>     liquid_float_complex *_y);
>     > void modem_get_demodulator_sample(modem _q, liquid_float_complex
>     > *_x_hat);
>     > %clear (liquid_float_complex *_y), (liquid_float_complex *_x_hat);
>     >
>     > This is an example from code I've written. This is documented in:
>     > http://www.swig.org/Doc4.0/SWIGDocumentation.html#Arguments_nn7
>     >
>     > Basically you write typemaps with generic names and then apply
>     them to
>     > your particular function arguments.
>     > Me personally, I like to clear %apply directives when I no
>     longer need
>     > them to avoid bugs to do "stray" typemaps.
>     >
>     > Hope it helped.
>     >
>     > Às 10:46 de 22/06/2020, Terry Barnaby escreveu:
>     >> I am wrapping a relatively complex C++ class library to produce a
>     >> Python interface. One thing I haven't worked out how to do is
>     to tell
>     >> SWIG to return certain function reference arguments on the lhs
>     of the
>     >> function call only, ie. assume them to be OUTPUT only
>     references. For
>     >> example (very simplified):
>     >>
>     >> class DataFile {
>     >>
>     >> public:
>     >>
>     >>     Error setInfo(const Info& info);    // Input only reference
>     >>
>     >>     Error getInfo(Info& info);        // Output only reference
>     >>
>     >> };
>     >>
>     >> Now I can rename the getInfo function in the C++ class library to
>     >> "Error getInfo(Info& OUTPUT);" say and add the appropriate
>     typemaps
>     >> to match this and that works, but I really don't want to rename
>     all
>     >> of the C++'s API function arguments for all of the classes in this
>     >> library (They are used for doxygen etc).
>     >>
>     >> This there a simple way in SWIG to override/rename the
>     arguments of a
>     >> particular function and/or particular classes member function ? So
>     >> something like:
>     >>
>     >> %rename("getInfo(Info& OUTPUT)") "getInfo(Info& info)"
>     >>
>     >> %rename("DataFile::getInfo(Info& OUTPUT)")
>     "DataFile::getInfo(Info&
>     >> info)"
>     >>
>     >>
>     >>
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