Lars Heber wrote:
I've got two other questions:1. Say we have a Class A with an attribute myObjects which is just a list. Now, I'd like to write my own Class B(A) - it extends A. But, in Class B, myObjects has to be a method because it has to be rebuild everytime it is called. So, how can I do something like: myObjects = getMyObjects() ? I tried to do this in the class itself, didn't work. Also tried self.myObjects = self.getMyObjects() - result wasn't what I wanted, myObjects got (of course) the resulting list of getMyObjects(), but I need myObjects to be a reference to getMyObjects()
I use a form of the following to compute dynamic titles for Zope objects, where the 'title' attribute is the result of a method call. Modifying it slightly for your case... from ComputedAttribute import ComputedAttribute Class B(A): def getMyObjects(self): ... myObjects = ComputedAttribute(lambda self: self.getMyObjects())
I'm not sure about this one, but I suspect an override of the __getattr__() method will let you intercept the lookup of the 'data' attribute, do any pre/post actions you wish, then return the real 'data'. You might try a ComputedAttribute arrangement instead and see if it works for your case since that would be easier. __getattr__2. Class A has another attribute, say data, which I want to control in Class B(A), i. e. everytime data is accessed (reading or writing), I want to intercept those actions. If it was just reading, I could use the strategy from 1., but I also want to control made changes to that attribute. Do I absolutely have to rewrite all the methods which access the wanted attribute, or is there another possibility with some kind of references, perhaps similar to software interrupts in DOS?
overrides can get into infinite loops w/o careful designs.
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