On 2019-10-19 12:37 AM, DL Neil via Python-list wrote:
On 16/10/19 6:33 PM, Frank Millman wrote:
On 2019-10-14 10:55 PM, DL Neil via Python-list wrote:
Is there a technique or pattern for taking a (partially-) populated
instance of a class, and re-creating it as an instance of one of its
sub-classes?
Here is a link to an article entitled 'Understanding Hidden Subtypes'.
It dates back to 2004, but I think it is still relevant. It addresses
precisely the issues that you raise, but from a data-modelling
perspective, not a programming one.
http://tdan.com/understanding-hidden-subtypes/5193
I found it invaluable, and applied the concepts in my own
business/accounting application. Having created the ability to make
subtypes visible and explicit, I found all kinds of unexpected uses
for them.
The article seems to be missing a couple of images (Figure 1 and
Figure 2) showing the data relationships. I downloaded the original
article onto my computer years ago, and my local copy does have the
images, so if you would like to see them let me know and I will upload
my version somewhere to make it accessible.
Superb!
Yes please Frank - I've also approached it from the data/DB side, and
thus presumably why I was puzzling over how one implements in Python.
(alternatively, email a PDF/similar directly)
Hi
I have just got back from a few days break and have only seen your
message now.
Did you see the message I posted on the 17th with a download link? If
not, would you like me to post it again?
Frank
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