Proxy

Proxy structural software pattern.

This module contains boiler-plate code to supply the Proxy structural software design pattern, to the client code.

class software_patterns.proxy.Proxy(proxy_subject: software_patterns.proxy.ProxySubject)

The Proxy has an interface identical to the ProxySubject.

Example

>>> from software_patterns import Proxy
>>> from software_patterns import ProxySubject

>>> class ClientProxy(Proxy):
...  def request(self, *args, **kwargs):
...   args = [args[0] + 1]
...   result = super().request(*args, **kwargs)
...   result += 1
...   return result

>>> proxied_operation = lambda x: x * 2
>>> proxy_subject = ProxySubject(proxied_operation)
>>> proxy_subject.request(3)
6

>>> proxy = ClientProxy(proxy_subject)
>>> proxy.request(3)
9

request(*args, **kwargs) → software_patterns.proxy.T

The most common applications of the Proxy pattern are lazy loading, caching, controlling the access, logging, etc. A Proxy can perform one of these things and then, depending on the result, pass the execution to the same method in a linked ProxySubject object.

class software_patterns.proxy.ProxySubject(callback: Callable[[...], software_patterns.proxy.T])

The ProxySubject contains some core business logic. Usually, ProxySubject are capable of doing some useful work which may also be very slow or sensitive - e.g. correcting input data. A Proxy can solve these issues without any changes to the ProxySubject’s code.

Example

>>> from software_patterns import ProxySubject
>>> proxied_operation = lambda x: x + 1
>>> proxied_operation(1)
2

>>> proxied_object = ProxySubject(proxied_operation)
>>> proxied_object.request(1)
2