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Recipe 184275: Automatic Delegation (Python) by Atsushi Odagiri
ActiveState Code (http://code.activestate.com/recipes/184275/)

1

Delegation gives us monotonous codings. But, special method '__getattr__' is called when a certain object does not have the called method.

This recipe solve the tiresome coding. The object should call delegated object's method by argument 'name'.

Python, 30 lines
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#!/usr/bin/env python

class Super:
    def methodA(self):
        print 'Super class methodA.'

class Delegated:
    def methodA(self):
        print 'Delegated class methodA.'

    def methodB(self):
        print 'Delegated class methodB.'

class X (Super):
    def __init__(self, delegate=None):
        self.delegate = delegate
    def __getattr__(self, name):

        return getattr(self.delegate, name)

delegated = Delegated()
x = X(delegated)
x.methodA()
x.methodB()


# Running this code.
# >> $ python delgate.py 
# >> Super class methodA.
# >> Delegated class methodB.

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Created by Atsushi Odagiri on Mon, 24 Feb 2003 (PSF)
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