[Chandler-dev] Future of redirectTo?
john at osafoundation.org
Wed Jul 26 09:59:43 PDT 2006
Grant Baillie wrote:
> Sure. But how exactly would this work: i.e. onValueChanged(),
> monitoring the changed values, or some other way? I'm a little wary of
> onValueChanged() becoming overly complex. In general, we want to index
> these attributes, so what I'd like to see is an API similar to what's
> now pim.Calculated:
> class MyContentItem(ContentItem):
> def getInterestingDatetime(self):
> # ... perform possibly complex calculation
> return resultOfPossiblyComplexCalculation
> # optional: setInterestingDatetime
> interestingDatetime = schema.IndexedProperty(
> basedOn = ('startTime', 'ticklers'),
> # basedOn == attributes in Indexed.addIndex()
> indexType = 'attribute', # could be
> fset = getInterestingDatetime)
> This would create an attribute which is a property on the class, and
> also create the appropriate index (named the same as the attribute).
> Maybe it somehow caches the value so that getInterestingDatetime
> doesn't get called every time the attribute is accessed (though it's
> not clear that's necessary).
> (FWIW, it's the index that ends up creating a monitor here to update
> when changes are made to the "source" attribute).
I'm also not in favor of using onValueChanged.
A simple implementation possibility would be to use a python property
for each source attribute involved in the complex calculation. It would
set the source attribute and call the complex calculation method that
might update the indexed attribute.
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