Re: [nimh-dev] virtual member functions

["Jon Stewart" <stew1@xxxxxxxxxxx>]

> Is there any way to make Python treat member functions overriden in a
> subclass as virtual? I'd like to add a parsesequence() to nimh.Message
> to override the one from mhlib.Message so I can add the remaining
> functionality to it, but when I try doing that Python seems not to notice
> and calls in mhlib.Message to parsesequence() still go to the one in
> mhlib.Message rather than my version in nimh.Message.


I thought parsesequence() was defined in folder? Anyway...

All functions can be overridden. From what I understand, Python is just a 
series of dictionaries acting as symbol tables. Each object gets its own 
symbol table -- you can actually add methods to an object that are unique 
to it. If python can't find the method in the object, it looks in the 
class' symbol table. If unsuccessful, it looks in the base class' symbol 
tables (depth first).

So, this should work:

class Base:
  def foo(self):
    print "bar"

class Derived(Base):
  def foo(self):
    print "baz"

x = Derived()
x.foo() # print baz

(This does work in the interpreter.)


Jon
-- 
Jon Stewart                                 Advanced Los Angeles C++
stew1@xxxxxxxxxxx                           http://www.alacpp.org
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