[PATCH 2 of 6] revlog: introduce _chunkbase to allow filelog to override

[Matt Mackall]

On Mon, 2011-02-07 at 11:27 +0100, Sune Foldager wrote:
> On 01-02-2011 00:44, Matt Mackall wrote:
> > On Mon, 2011-01-31 at 11:21 +0100, Sune Foldager wrote:
> >> # HG changeset patch
> >> # User Sune Foldager<cryo at cyanite.org>
> >> # Date 1296294467 -3600
> >> # Node ID 228f2570b1922c797b969dab28a28e3f1ec99cf7
> >> # Parent  90afd2364f5d05afe149156379fc3ee6dfd604fe
> >> revlog: introduce _chunkbase to allow filelog to override
> >>
> >> Used by revlog.revision to retrieve the base-chunk in a delta chain.
> >
> > Still not clear on why this is better than the normal superclass
> > technique.
> 
> Hmm.. what do you mean? Not sure I follow completely :/

Your code does something like this with _chunkbase:

class a(object):
  def foo(self):
    return "a"
  bar = foo  # let us override foo
  def baz(self):
    print self.bar() # knows about override potential

class b(a):
  def foo2(self):
    # combine behavior from a and b
    return self.foo() + "b"
  bar = foo2

The normal 'superclass' approach is:

class a(object)
  def foo(self):
    return "a"
  def baz(self):
    print self.foo()

class b(b):
  def foo(self):
    return super(b, self).foo() + "b"

-- 
Mathematics is the supreme nostalgia of our time.