delegation_pattern.py

"""
Reference: https://en.wikipedia.org/wiki/Delegation_pattern
Author: https://github.com/IuryAlves

*TL;DR
Allows object composition to achieve the same code reuse as inheritance.
"""

from __future__ importannotations

fromtypingimportAny, Callable


classDelegator:
"""
 >>> delegator = Delegator(Delegate())
 >>> delegator.p1
 123
 >>> delegator.p2
 Traceback (most recent call last):
 ...
 AttributeError: 'Delegate' object has no attribute 'p2'
 >>> delegator.do_something("nothing")
 'Doing nothing'
 >>> delegator.do_anything()
 Traceback (most recent call last):
 ...
 AttributeError: 'Delegate' object has no attribute 'do_anything'
 """

def__init__(self, delegate: Delegate) ->None:
self.delegate=delegate

def__getattr__(self, name: str) ->Any|Callable:
attr=getattr(self.delegate, name)

ifnotcallable(attr):
returnattr

defwrapper(*args, **kwargs):
returnattr(*args, **kwargs)

returnwrapper


classDelegate:
def__init__(self) ->None:
self.p1=123

defdo_something(self, something: str) ->str:
returnf"Doing {something}"


if__name__=="__main__":
importdoctest

doctest.testmod()