[Tutor] Changing a class into a subclass

Max Noel maxnoel_fr at yahoo.fr
Thu Mar 24 19:30:34 CET 2005

On Mar 24, 2005, at 18:07, Ismael Garrido wrote:

> Hello.
> I have a program that saves/loads to/from XML. I have a main class 
> Building, and a subclass House(Building). When I save the code I 
> instruct each object to save itself to XML (using ElementTree), so 
> House adds itself to the XML tree.
> My problem is when I load the XML. Before having subclasses what I did 
> was to send the XML object (again in ElementTree) to the object and 
> let itself load. Now, with subclasses, if I send the House XML to 
> Building I get a Building instance, when I need a House instance.

	You can't make an object transform into an object of a different 
class. You need to identify what class the object will be an instance 
of before loading it. Which, if you're using XML tags like <Building 
type="House"> or <House>, shouldn't be very difficult to do.

-- Max
maxnoel_fr at yahoo dot fr -- ICQ #85274019
"Look at you hacker... A pathetic creature of meat and bone, panting 
and sweating as you run through my corridors... How can you challenge a 
perfect, immortal machine?"

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