Re: Derived class getattro

[Fernando L. <fer...@gm...>]

But derivarion works fine with old Style classes.

Today i was thinking in make the whole class hierarchy with old style
ones and restrict new style to some particular aspects of the
simulator (e.g. a system container that doesn't derive from Block)

Best regards
Fernando

2010/4/12, Barry Scott <ba...@ba...>:
>
> On 10 Apr 2010, at 19:34, Fernando Libonati wrote:
>
>> In cxx_extensions.cxx
>>
>> extern "C" PyObject *getattro_handler( PyObject *self, PyObject *name )
>> {
>>     try
>>     {
>>         PythonExtensionBase *p = getPythonExtensionBase( self );
>>         return new_reference_to( p->getattro( Py::String( name ) ) );
>>     }
>>     catch( Py::Exception &)
>>     {
>>         return NULL;    // indicate error
>>     }
>> }
>>
>> In a derived class this always call the getattro of the base class, and
>> never get the derived class attributes visible.
>> How can I access a derived class attro?
>>
>> I've attached the test system, base.h and base.cxx.
>> When compiled, it is possible to create a g = base.Gain("b",1,None,2.43)
>> object, and access name,number and parent attributes, but doesn't reach
>> the gain attribute.
>> Python says
>> """Traceback (most recent call last):
>>   File "<stdin>", line 1, in <module>
>> AttributeError: 'Gain' object has no attribute 'gain'
>> """
>>
>> It would be possible to call first the derived class method, and inside it
>> call the base class method (under the user responsibility)?
>
> You cannot use C++ derivation to create a set of Python types.
>
> When Block is setup there are a lot of python data structures created and
> initialise to make Block available to Python.
>
> Gain has none of these python data structures.
>
> If you want  a hierarchy of classes then only the leafs can be turned into
> Python classes.
>
> Barry
>
>
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-- 
Fernando Libonati
fernando.libonati at gmail.com