"""Proxy structural software pattern.
This module contains boiler-plate code to supply the Proxy structural software
design pattern, to the client code."""
from abc import ABC
from typing import Generic, TypeVar
T = TypeVar('T')
__all__ = ['Proxy']
class ProxySubjectInterface(ABC):
"""Proxy Subject interface holding the important 'request' operation.
Declares common operations for both ProxySubject and
the Proxy. As long as the client uses ProxySubject's interface, a proxy can
be passed pass to it, instead of a real subject.
"""
[docs]class Proxy(ProxySubjectInterface, Generic[T]):
"""
The Proxy has an interface identical to the ProxySubject.
Example:
>>> from software_patterns import Proxy
>>> class PlusTen(Proxy):
... def __call__(self, x: int):
... result = self._proxy_subject(x + 10)
... return result
>>> def plus_one(x: int):
... return x + 1
>>> plus_one(2)
3
>>> proxy = PlusTen(plus_one)
>>> proxy(2)
13
"""
def __init__(self, runtime_proxy: T):
self._proxy_subject = runtime_proxy
def __getattr__(self, name: str):
return getattr(self._proxy_subject, name)
def __str__(self):
return str(self._proxy_subject)
def __hash__(self):
return hash(self._proxy_subject)