Re: [pygccxml-development] How to manage wrapper classes?

[Matthias B. <ba...@ir...>]

Roman Yakovenko wrote:
> Lets skip the rest. Here is what I propouse to you:
> http://boost.org/libs/python/doc/v2/faq.html#custom_string

Oops, I missed that one!
I've just tried it out and it works like a charm. Thanks!

Now that this problem is solved there's already the next one which is 
somewhat related and which, I believe, needs a different solution.

In the Maya SDK error handling is done with MStatus objects which carry 
error information (C++ exceptions are never used). There are two 
possibilities how a SDK function returns a result object. It either 
returns a MStatus object as in the following example:

MStatus select(MObject& object);

or it expects an optional pointer to a MStatus object as input which it 
uses to set its status information:

bool isSelected(MObject& object, MStatus* ReturnStatus=NULL);

So far, the Python bindings just work like the C++ version. But what I 
would actually like to have is that the Python version may raise an 
exception when an error occurs, no matter if the user provided a MStatus 
object or not.
I suppose in the first case where the function returns a MStatus object 
I could probably "abuse" a result converter to check for an error 
instead of converting the value (I haven't tried that out yet). But for 
the second case I think it requires a wrapper because I need to place 
code before and after the actual function call, something like:

bool isSelected_wrapped(MObject& object, MStatus* ReturnStatus=NULL)
{
   MStatus internalstat;
   MStatus* finalstat=&internalstat;
   // If the user provided a MStatus object then use this one...
   if (ReturnStatus!=NULL)
   {
     finalstat = ReturnStatus;
   }

   // Call the original function...
   bool res = isSelected(object, finalstat);

   // Check for errors...
   if (exceptions_enabled && finalstat->error())
   {
     throw AnAppropriateException();
   }
   return res;
}

So how should that be accomplished? (and how can it be guaranteed that 
the user's wrapper code doesn't interfere with the wrapper code that 
might already get generated by pyplusplus?)

- Matthias -