Re: [Traits] feature request

G'day,

Prabhu Ramachandran wrote:
> Hi Dave Morrill,
> 
> I see from the implementation (from trunk) that the CHasTraits class 
> defines a _trait_change_notify method that is used in the trait_set 
> method to disable/enable notifications.  Unfortunately, there is no way 
> to determine from Python if this flag has been set or not.  This is 
> needed if you want to create a Property trait that does the right thing 
> in its set method.  For example:
> 
> class Test(HasTraits):
>     x = Property(Float)
>     _x = Float
>     def _get_x(self):
>     return self._x
>     def _set_x(self, value):
>     old = self._x
>     self._x = value
>     if old != new:
>         self.trait_property_changed('x', old, new)
> 
> Clearly, this will break the trait_set method when 
> trait_change_notify=False.  I propose to add a 
> _get_trait_change_notify() to the ctraits.c to be able to get this so 
> users can write:
> 
>  if self._get_trait_change_notify():
>      ...
> 
> etc. to work around this.

Hmmm... I wouldn't want to have to put this line in every property setter... smells like 
duplication... Couldn't the 'trait_property_changed' method handle the check?

Martin