[pygtk] Overriding interface properties

[Just Fill Bugs]

On 06/17/2011 05:05 PM, Arjan Molenaar wrote:
>
> On 17 Jun 2011, at 05:25, Just Fill Bugs wrote:
>
>> On 06/17/2011 12:44 AM, Arjan Molenaar wrote:
>>> Hi,
>>>
>>> I've started porting Gaphas to GTK+ 3 now, using PyGI on Linux. It all goes quite smoothly. Only now I'm running
>>> into the problem that my widget should implement the Gtk.Scrollable interface. For that it should define
>>> a few properties.
>>>
>>> In C those need to be declared using g_object_class_override_property(). What's the Python counterpart for this?
>>>
>>
>> It seems the PyGobject examples/properties.py works okey once you replaced gobject with GObject to make it gi compatible. So take a look at the PyGobject's examples directory.
>
> Did that. Only there the creation of new properties is demoed. I need to implement properties defined in an interface. For that the protocol is slightly different. I can't find how that is covered.
>

Aha, looking into pygobject source tree under the 
tests/test_properties.py, it shows how to do the getter/setter in the
class TestProperty(unittest.TestCase):

     def testCustomGetter(self):
         class C(gobject.GObject):
             def get_prop(self):
                 return 'value'
             prop = gobject.property(getter=get_prop)

         o = C()
         self.assertEqual(o.prop, 'value')
         self.assertRaises(TypeError, setattr, o, 'prop', 'xxx')

     def testCustomSetter(self):
         class C(gobject.GObject):
             def set_prop(self, value):
                 self._value = value
             prop = gobject.property(setter=set_prop)

             def __init__(self):
                 self._value = None
                 gobject.GObject.__init__(self)

         o = C()
         self.assertEquals(o._value, None)
         o.prop = 'bar'
         self.assertEquals(o._value, 'bar')
         self.assertRaises(TypeError, getattr, o, 'prop')

So you have to specify getter/setter when declare properties at 
gobject.property().

Someone should make a better example for the new style property 
specification in the doc.