[Gdal-dev] SWIG / TestCapability / Ruby

[Charlie Savage]

The various TestCapability methods in OGR have a return type of integer. 
  However, if you read the OGR C API documentation its says:

"Returns: TRUE if the layer has the requested capability, or FALSE 
otherwise. OGRLayers will return FALSE for any unrecognized capabilities."

So it seems like the intent it to return a boolean.  In C-like languages 
returning an int is ok, since 0 evaluates to false.

This however, is not the case in all languages.  In Ruby, for example, 
false is either nil (same as NULL or PyNone) or false.  Thus the value 0 
does *not* evaluate to false.  That means you can't do something what is 
natural:

if lyr.test_capability( 'FastGetExtent')

It will always evaluate to true in Ruby!

I would like to change the SWIG wrapper code so that all the 
testcapability methods return booleans.  I think this is ok, since the 
bindings are built using SWIG's C++ mode, so boolean is a supported data 
type.  That way I don't have to put in a separate mapping for these 
methods just in the Ruby bindings.

Thanks,

Charlie