65 lines
1.8 KiB
Python
65 lines
1.8 KiB
Python
import importlib
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from abc import ABC, abstractmethod
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# 抽象主题
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class Subject(ABC):
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@abstractmethod
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def request(self):
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pass
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# 真实对象 1
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class RealSubjectA(Subject):
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def request(self):
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print("RealSubjectA: Handling request.")
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# 真实对象 2
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class RealSubjectB(Subject):
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def request(self):
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print("RealSubjectB: Handling request.")
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# 默认代理（备用对象）
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class DefaultSubject(Subject):
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def request(self):
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print("DefaultSubject: Handling request as fallback.")
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# 代理对象
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class Proxy(Subject):
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def __init__(self, real_class_name: str):
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self._real_subject = self._create_real_subject(real_class_name)
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def request(self):
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print("Proxy: Additional logic before delegating.")
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self._real_subject.request()
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print("Proxy: Additional logic after delegating.")
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@staticmethod
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def _create_real_subject(class_name: str) -> Subject:
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# 动态加载类
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try:
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cls = globals().get(class_name) # 从当前全局作用域中获取类
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if cls is None:
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raise KeyError
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if not issubclass(cls, Subject):
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raise TypeError(f"{class_name} is not a subclass of Subject.")
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return cls()
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except (KeyError, TypeError):
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print(f"Warning: Class '{class_name}' not found or invalid. Using DefaultSubject.")
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return DefaultSubject()
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# 客户端代码
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def client_code(proxy: Proxy):
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proxy.request()
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# 使用代理，通过字符串指定真实类
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print("Client: Using RealSubjectA:")
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proxy_a = Proxy("RealSubjectA")
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client_code(proxy_a)
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print("\nClient: Using RealSubjectB:")
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proxy_b = Proxy("RealSubjectB")
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client_code(proxy_b)
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print("\nClient: Attempting to use a non-existent class:")
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proxy_invalid = Proxy("NonExistentClass")
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client_code(proxy_invalid)
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