The difference between getattr and restrictedTraverse

[Martin Aspeli]

Hi Tim,

Tim Hicks wrote:
> Tom Lazar wrote:
> 
>>> What I'm trying to do now is make it so that methods on my weblog object
>>> will return lists of IWeblogEntry-ish objects that know what sort of URL
>>> they should have.  That way, I can call IWeblog.getLazyEntries(), which
>>> does a catalog search for appropriate IWeblogEntry objects, and then
>>> call absolute_url (or getURL) on each of the returned objects and have
>>> it return a blog-archive-ish URL rather than where it really lives.
>> IMHO this is not a good approach as it blurs the boundary between
>> content and representation. why should a (weblog entry) object 'know'
>> what its display url is? what if you change the mapping? you would have
>> to change your code...
> 
> I take your point.  In response to your "why should a (weblog entry)
> object 'know' what its display url is?", I'd say "because people expect
> it to".  That is, 'absolute_url' is the recognised way of retrieving an
> object's url.  In essence, my question to you might be "why should a
> developer have to use a special API to get the appropriate url of an
> object when there is a perfectly good, and widely-known, zope API method
> already?".

Please. Do *not* try to re-define the meaning of absolute_url. It has a 
very specific purpose and meaning, and changing it would likely cause 
(a) confusion and (b) subtle breakage. I know it sounds "neat" that the 
pseuo-url is returned from "the" URL function, but it's not a good idea. 
Leave it alone. Please.

>>From your objection above, it sounds like you would favour declaring a
> view for IWeblogEntry objects (and their catalog brains) that provides,
> say, a getArchiveURL method.  That's what Martijn (Pieters) was suggesting.

+1

> Taking the approach that I have pursued at
> <http://dev.plone.org/collective/browser/Quills/branches/maurits-traversal/traversalfaker.py>,
> I can have code that looks like::
> 
>   <div tal:repeat="entry weblog/getLazyEntries">
>     <a tal:attributes="href entry/getURL"
>        tal:content="entry/Title">title</a>
>   </div>
> 
> This compares to what I envisage the view approach looking like::
> 
>   <div tal:repeat="brain weblog/getLazyEntries">
>     <a tal:define="weblogentryview brain/@@weblogentryview"
>        tal:attributes="href weblogentryview/getArchiveURL"
>        tal:content="brain/Title">title</a>
>   </div>
> 
> Maybe the latter is better simply because it is less "magic" and I'm
> over-estimating the down-side of not using the standard API.

+100

I guarantee you that there will be times when you'll need the "real" URL 
as well, and if absolute_url() doesn't return it, you have no way of 
getting to it.

Also see my sig.

Martin

-- 
Acquisition is a jealous mistress