Re: [Gramps-devel] Properties and private attributes, vs. just regular attributes

[Doug B. <dou...@gm...>]

On Thu, Nov 5, 2009 at 7:12 AM, Benny Malengier
<ben...@gm...> wrote:
> 2009/11/5 Doug Blank <dou...@gm...>:
>> Benny,
>>
>> I see that in the plugin objects that you have things like:
>>
>>   ...
>>        self._fname = None
>>
>>    def _set_fname(self, fname):
>>        self._fname = fname
>>
>>    def _get_fname(self):
>>        return self._fname
>>
>>    fname = property(_get_fname, _set_fname)
>>
>> I see no advantage of doing all of that over just having an attribute.
>> Why do this?
>
> One way to do all of them.
> For fname, I cannot think of a reason some plugin would not have it,
> but as you can see in the others, this construct is used for error
> checking in the function on assign. We could do with fname also, is
> the file ended by '.py', does it exist, ...,
> and raise error on problem.
> So the register code can not just assign whetever it wants to a
> plugindata object, everything that is assigned goes through a
> function, allowing for control on what the plugin wants to register.
>
> Anyway, the suggestion comes from Richard, I think he is used to doing
> it like that. Working with slots you could now optimize the class
> object I think.
>
> Note that I don't want to have extra attributes created on the object
> outside of what is defined in the init (as your old gramplet register
> code could do), so just assigning should raise an error, which in the
> register function is taken care of by the gettattr call, this will
> give an error if the attribute was not created in the init method of
> plugindata.

Ok, thanks for the explanation. I'm not a big fan of doing this kind
of checking (types, proper attributes, etc.) but I am a fan of unit
tests. I think the test for getattr is a good idea. (As an aside, this
property philosophy would seem to argue for the register function,
don't you think?)

In any event, I've added fname as a property for all plugins and
help_url property for gramplets.

-Doug

> Benny
>
>>
>> -Doug
>>
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