John M. Gabriele a écrit :
> Consider the following:
>
> #!/usr/bin/python
>
> #-----------------------------------------------------------------
> class Grand_parent( object ):
>
> def speak( self ):
> print 'Grand_parent.speak()'
> self.advise()
>
> def advise( self ):
> print 'Grand_parent.advise()'
> self.critique()
>
> def critique( self ):
> print 'Grand_parent.critique()'
>
>
> #-----------------------------------------------------------------
> class Parent( Grand_parent ):
>
> def speak( self ):
> print '\tParent.speak()'
> self.advise()
>
> def advise( self ):
> print '\tParent.advise()'
> self.critique()
>
> # ATM, the Parent is at a loss for words, and has no critique.
>
>
> #-----------------------------------------------------------------
> class Child( Parent ):
>
> def speak( self ):
> print '\t\tChild.speak()'
> self.advise()
>
> # Currently, the Child has no really useful advice to give.
>
> def critique( self ):
> print '\t\tChild.critique()'
>
>
> #-----------------------------------------------------------------
> print 'speak() calls advise(), then advise() calls critique().'
> print
>
> people = [ Grand_parent(), Parent(), Child() ]
> for person in people:
> person.speak()
> print
>
>
>
> ====================
> The output is:
>
> speak() calls advise(), then advise() calls critique().
>
> Grand_parent.speak()
> Grand_parent.advise()
> Grand_parent.critique()
>
> Parent.speak()
> Parent.advise()
> Grand_parent.critique()
>
> Child.speak()
> Parent.advise()
> Child.critique()
>
>
> What's going on here with that last "Child.critique()"? The
> Parent called self.critique(), and since it *had* no critique()
> method, it should've deferred to it's parent's critique()
> method, right? But instead, somehow Child.critique() got called.
> Why?
>
> ---J
>
Because that's the way virtual methods are supposed to work. When you
can a methon foo on an object, you always start your search from the
current object class and not the class of the current function.
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