67 lines
1.7 KiB
Python
67 lines
1.7 KiB
Python
import threading
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from dataclasses import dataclass
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class ParameterizedSingletonMeta(type):
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"""
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参数化单例元类
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行为：
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- 相同 (类, args, kwargs) → 同一实例
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- 不同参数 → 不同实例
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"""
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_instances: dict = {}
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_lock = threading.RLock()
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def __call__(cls, *args, **kwargs):
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# 1. kwargs 排序，保证顺序无关
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kwargs_key = tuple(sorted(kwargs.items()))
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# 2. 构造不可变的 key
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key = (cls, args, kwargs_key)
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# 3. 防御：确保所有参数都可 hash
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try:
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hash(key)
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except TypeError as e:
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raise ValueError(
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f"{cls.__name__} 的单例参数必须全部可 hash"
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) from e
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with cls._lock:
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if key not in cls._instances:
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cls._instances[key] = super().__call__(*args, **kwargs)
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else:
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print(f"[HIT] 命中缓存实例: {key}")
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return cls._instances[key]
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@classmethod
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def get_all_instances(cls):
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"""调试用：返回当前已创建的所有实例"""
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return list(cls._instances.values())
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@dataclass
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class Demo(metaclass=ParameterizedSingletonMeta):
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"""
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示例：参数化单例对象
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"""
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name: str
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def __post_init__(self):
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print(f"正在初始化 Demo(name={self.name})")
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def __str__(self):
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return f"<Demo name={self.name} id={id(self)}>"
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if __name__ == "__main__":
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print("=== 测试 1：相同参数 ===")
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d1 = Demo(name="config_A")
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d2 = Demo(name="config_A")
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print(d1)
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print(d2)
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print("是否同一实例：", d1 is d2)
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print(ParameterizedSingletonMeta.get_all_instances()) |