At Thursday 24/8/2006 16:23, Chaz Ginger wrote:
I was writing some code that used someone else class as a subclass. He
wrote me to tell me that using his class as a subclass was incorrect. I
am wondering under what conditions, if ever, does a class using a
subclass not work.
class B1(A);
def __init__(self,a1,a2) :
self.c = a1
A.__init__(self,ag)
class B2:
def __init__(self,a1,a2):
self.c = a1
self.t = A(a2)
def bar(self) :
self.t.bar()
Other than the obvious difference of B2 having an attribute 't', I can't
see any other obvious differences. Is there something I am missing?
Look any OO book for the difference between 'inheritance' and
'delegation'. In short, you should inherit when B 'is an' A (a Car is
a Vehicle), and delegate/compose in other cases (a Car has an Engine;
or more precisely, a Car instance has an Engine instance).
Gabriel Genellina
Softlab SRL
p5.vert.ukl.yahoo.com uncompressed Thu Aug 24 19:27:05 GMT 2006
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