wxruby users - Sep 2006 - [Fwd: Re: [Swig-user] wrapping enums for python]

Take a look at this message thread.  I think it would be 
interesting/nice if our constants and enums also returned a nice name 
when inspected.

Thoughts?

Roy

-------- Original Message --------
Subject: 	Re: [Swig-user] wrapping enums for python
Date: 	Wed, 13 Sep 2006 17:14:50 +0200
From: 	Nitro <nitro@dr-code.org>
To: 	K M <intra611@gmail.com>, swig-user@lists.sourceforge.net
References: 	<194b4da90609130632h66c62ed8o8035b4bc041fdb79@mail.gmail.com>



Am 13.09.2006, 15:32 Uhr, schrieb K M <intra611@gmail.com>:
> Hi,
>
> When printing enum wrapped to python I would like to get symbol instead  
> of
> number. For example
>
> in C++:
>
> enum min_max
> {
>     SS_MIN = 0,
>     SS_MAX = 100
> };
>
>
> I get:
>
> print swigtest.SS_MAX
> 100
>
> and I would like to get:
>
> print swigtest.SS_MAX
> SS_MAX
>
> So the idea was to use something like:
>
> %pythoncode %{
>
> class Enum(int):
>     def __new__(cls, arg, desc ):
>         self = int.__new__(cls, arg)
>         self.desc = desc
>         return self
>     def __repr__( self ):
>         return self.desc
>
> %}
>
> and then somehow in the .py file
>
> SS_MIN = Enum(_swigtest.SS_MIN, "SS_MIN")
> instead of
> SS_MIN = _swigtest.SS_MIN
>
> But the problem is that I do not know how to do
> SS_MIN = Enum(_swigtest.SS_MIN, "SS_MIN")
> for each define (would it be possible to use something like
> %feature("pythonprepend")?) .
>
> Also there are C++ methods that return enums so it might be necessary to
> create Enum python class  in wrapper cxx file instead of py file.
> (And then change SWIG_Python_SetConstant() method to create equivalent of
> SS_MIN = Enum(_swigtest.SS_MIN, "SS_MIN") ).
>
> As I am new to SWIG (and Python as well) I wander if there is better and
> simpler way how to do this.
>
> Thanks
Maybe you can take a look here  
http://www.swig.org/Doc1.3/Typemaps.html#Typemaps_nn7 under point "Return  
value handling". You could then write a typemap which converts the  
returned enum to a Enum class.
You could probably use %pythoncode to insert your python statement into  
the .py file. Just make sure you put it at the very end of your interface  
file.
You probably even don''t have to specify any of the enums by hand, just
use
swig''s xml output and parse it to generate some code that applies your
enum typemap to all enums in your code. How to do this xml/parse thing was  
several times on the mailing lists, search for xml and robin dunn  
probably. The last post was not more than a month ago.
All in all I really like your idea, I thought about something similar some  
way back. You could extend your Enum class to cover operations such as  
or''ing together some elements (like const1 | const2).
Personally I''d like to see this approach here as standard swig
behaviour.
What do you (other language maintainers for example) think?

-Matthias

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Roy Sutton wrote:
> Take a look at this message thread.  I think it would be 
> interesting/nice if our constants and enums also returned a nice name 
> when inspected.
>   
Yes. A string or symbol would be much more useful.

The use of integer constant ids throughout wxRuby is a bane. e.g. When 
describing a menu item you have to mention the thing three times 
(declare constant; add menu item; hook event).

I tried ameliorating this by using Ruby symbols for menu ids (more 
readable, literal and have a guaranteed unique conversion to integer), 
but the integers choked Wx...

alex