Donn Ingle a écrit :
>>>I thought this might be a case for multiple inheritance
>>
>>???
>
> Well, in terms of having Canvas and Thing inherit from Stack and thereby
> (somehow, not sure how) they would both have access to Stack.stack (a list)
>
>
>>wrt/ all Thing instances having to refer to a same Stack instance,
>>there's a pretty obvious answer: make the Stack instance an attribute of
>>class Thing, ie:
>>class Thing(object):
>> stack = Stack()
>>
>> def some_method(self, val):
>> self.stack.push(val)
>> # etc...
>
>
> No can do:
> Canvas ---> Stack <--- Thing
Sorry but you're exemple is using classes, not instances. So while *you*
may know what you mean, it's not decidable for me.
> Both Canvas and Thing have to use the same Stack.
You mean: both Canvas class and Thing class have to use the same Stack
Class ? Or : for all Canvas instances and all Thing instances, there
must be only one same Stack instance ? Or: a given (Canvas instance,
Thing instance) couple must share a same Stack instance ? Or (etc...)
> It gets things pushed onto
> it by them both.
Both what ? classes ? instances ?-)
>
>>Now the point that isn't clear is the exact relationship between Stack
>>and Canvas. You didn't give enough details for any answer, advice or
>>hint to make sens.
>
> Sorry, didn't want to write an overly long post.
There's certainly a balance between being overly vague and being overly
long !-)
> a Canvas holds many Things (graphics) and it pushes each Thing onto the
> Stack. The Things also push data onto the same Stack. After that the Stack
> pops and draws each Thing to the screen.
>
> What I'm asking about is subtle and I don't know how to word it: how can
> Classes
I guess you mean "instances", not "classes".
> share common objects without using global variables specifically
> named within them?
Err...Perhaps a dumb question, but what about passing the "common
objects" to initializers ?
> ## == API in another module perhaps ===
> Class Stack:
> def push(self,stuff):
> pass
>
> Class Canvas:
> def do(self):
> s.push("data") #I don't feel right about 's' here.
>
> Class Thing:
> def buzz(self):
> print s.pop(0)
>
> ## == User space code area ===
> s = Stack() #I want to avoid this direct naming to 's'
> c = Canvas()
> c.push("bozo")
> t = Thing()
> t.buzz()
# API land
class Stack(object):
# ok, we all know what a stack is
class Canvas(object):
def __init__(self, stack):
self.stack = stack
def do(self):
self.stack.push("data")
class Thing(object):
def __init__(self, stack):
self.stack = stack
def buzz(self):
print self.stack.pop(0)
# Userland
s = Stack()
c = Canvas(s)
t = Thing(s)
c.do()
t.buzz()
HTH
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