barbaros a écrit :
On Apr 23, 10:48 am, Bruno Desthuilliers <bruno.
[EMAIL PROTECTED]> wrote:
My question is: can it be done using inheritance ?
Technically, yes:
class OrientedBody(Body):
def __init__(self, orient=1):
Body.__init__(self)
self.orient = 1
Now if it's the right thing to do is another question...
If I understand correctly, in the above implementation I cannot
define firstly a (non-oriented) body, and then build, on top of it,
two bodies with opposite orientations. The point is, I want
both oriented bodies to share the same base Body object.
Then it's not a job for inheritence, but for composition/delegation -
Sorry but I didn't get your specs quite right :-/
Now the good news is that Python makes composition/delegation close to
a no-brainer:
class Body(object):
# definitions here
class OrientedBody(object):
# notice that we *dont* inherit from Body
def __init__(self, body, orient):
self._body = body
self.orient = orient
def __getattr__(self, name):
try:
return getattr(self._body, name)
except AttributeError:
raise AttributeError(
"OrientedBody object has no attribute %s" % name
)
def __setattr__(self, name, val):
# this one is a bit more tricky, since you have
# to know which names are (or should be) bound to
# which object. I use a Q&D approach here - which will break
# on computed attributes (properties etc) in the Body class -
# but you can also define a class attribute in either Body
# or OrientedBody to explicitly declare what name goes where
if name in self._body.__dict__:
setattr(self._body, name, val)
else:
object.__setattr__(self, name, value)
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