[Xapian-discuss] Using a subclass of MatchSpy in Python bindings

[Doctor Munchkin]

On 1 December 2010 21:52, Olly Betts <olly at survex.com> wrote:
> On Wed, Dec 01, 2010 at 01:18:40PM +0000, Doctor Munchkin wrote:
>> >>> class MyMatchSpy(xapian.MatchSpy):
>> ...     def __init__(self):
>> ...             pass
>> ...     def __call__(self, *args, **kw):
>> ...             print "called with", args, kw
>> ...
>> >>> ms = MyMatchSpy()
>> >>> enquire = xapian.Enquire(database)
>> >>> enquire.add_matchspy(ms)
>> Traceback (most recent call last):
>>   File "<stdin>", line 1, in <module>
>>   File "/usr/lib/python2.6/dist-packages/xapian/__init__.py", line
>> 6920, in _enquire_match_spy_add
>>     _enquire_add_matchspy_orig(self, decider)
>> TypeError: in method 'Enquire_add_matchspy', argument 2 of type
>> 'Xapian::MatchSpy *'
>>
>> Am I missing something obvious here, or is swig misbehaving? The above
>> works if ms is an instance of xapian.ValueCountMatchSpy, but I need to
>> implement something different to this.
>
> I think you need to call the base class constructor in your constructor:
>
>    def __init__(self):
>        xapian.MatchSpy.__init__(self)
>

Hi Olly, thanks for the quick response.

When I try that, I get an error from MatchSpy's __init__:

>>> database = xapian.Database(dbpath)
>>>
>>> class MyMatchSpy(xapian.MatchSpy):
...     def __init__(self):
...         xapian.MatchSpy.__init__(self)
...     def __call__(self, *args, **kw):
...         print "called with", args, kw
...
>>> ms = MyMatchSpy()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 3, in __init__
  File "/usr/lib/python2.6/dist-packages/xapian/__init__.py", line
3201, in __init__
    def __init__(self, *args, **kwargs): raise AttributeError("No
constructor defined")
AttributeError: No constructor defined

It looks like swig deliberately forbids subclassing of MatchSpy. Is
there a way around this?

Thanks,

Munchkin