On Fri, 9 Nov 2012 14:05:01 +0800
Russell Keith-Magee <russ...@keith-magee.com> wrote:
> Why on earth can't just just take the logic that you're putting in init(),
> and put it *in dispatch()*. The sequence of calls is *identical*, and since
> *args and **kwargs are locals, they don't need to be set anywhere. What's
> the problem with putting the init() logic in the dispatch() method in the
> way I described?
I think the problem is that order of initialization _is_ reversed when
inheritance comes into the game, in the case of handling everything at
the beginning of dispatch(). Consider:
class DepartmentMixin(object):
def initialize(self, request, *args, **kwargs):
super(DepartmentMixin, self).initialize(request, *args, **kwargs)
self.department = get_object_or_404(Department,
slug=kwargs['department'])
class ShiftMixin(DepartmentMixin):
def initialize(self, request, *args, **kwargs):
super(ShiftMixin, self).initialize(request, *args, **kwargs)
self.shift = get_object_or_404(Shift, department=self.department,
datetime__year=kwargs['year'])
This would not be possible in dispatch() because the super method must
be called at the end of the child method (tail recursion):
class DepartmentMixin(object):
def dispatch(self, request, *args, **kwargs):
self.department = get_object_or_404(Department,
slug=kwargs['department'])
return super(DepartmentMixin, self).dispatch(request, *args, **kwargs)
class ShiftMixin(DepartmentMixin):
def initialize(self, request, *args, **kwargs):
# THIS DOESN'T WORK: self.department HAS NOT BEEN SET YET.
self.shift = get_object_or_404(Shift, department=self.department,
datetime__year=kwargs['year'])
return super(ShiftMixin, self).dispatch(request, *args, **kwargs)
I think the control flow is easier to follow in case of initialize()
vs. dispatch(). This doesn't mean that I think initialize() should be
part of core, but the described situation is something I came across in
real life.
Best wishes,
Sebastian.
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