Q? Calling nearest inherited method

[Thomas Wouters]

On Wed, May 17, 2000 at 11:54:53AM +0000, Oleg Broytmann wrote:
> On Wed, 17 May 2000, Laurent POINTAL wrote:
> > Given a class hierarchy like this:
> > A
> > B inherits A
> > C inherits B
> > 
> > A define dothis method.
> > C define dothis method.
> > 
> > In the C.dothis, I wants to call my nearest parent class dothis
> > method. That is, call B.dothis if it is defined, or A.dothis if it is
> > defined...

>    I think B.dothis() will do it just right, no?

Yes, but dont forget to manually pass 'self' (or whatever you call the first
argument in your method.)

class C(B):
	def dothis(self, x):
		# your code here
		B.dothis(self, x)
		# more code here

If you aren't sure if B has a 'dothis' method (either from itself or
inherited) wrap the call in a try/except. And if you dont want to hard-code
the name of the parent class in more than one place (the class line), use
self.__class__.__bases__. This is a tuple containing the base classes for
that class. If you want to call all possible dothis() methods, in all
parents, you could do something like this:

def dothis(self, *args, **kwargs):
	for parent in self.__class__.__bases__:
		try:
			method = parent.dothis
		except AttributeError:
			continue
		apply(method, (self,)+args, kwargs)

or if you just want to call the first one you find, either change the last
line to 'return apply ...' or add a 'break' after the 'apply'.

-- 
Thomas Wouters <thomas at xs4all.net>

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