Python混入类高级设计

"""Python混入类高级设计——Mixin、ABC 与协作式 super()
------------------------------------------------------------------------------
Mixin 通过多重继承组合可复用行为。结合 ABC 抽象约束和 cooperative super()
调用，可实现灵活优雅的类层次。关键是 Mixin 间用 **kwargs 协作不阻塞链。
"""

from abc import ABC, abstractmethod
from typing import Any, Dict


# ========== 1. 基础 Mixin：注入能力 ==========

class LogMixin:
"""混入日志记录能力"""
def log(self, msg: str, level: str = "INFO") -> None:
print(f"[{level}] {self.__class__.__name__}: {msg}")

class UserService(LogMixin):
def create(self, name: str) -> None:
self.log(f"创建用户：{name}")


# ========== 2. Mixin + ABC 抽象约束 ==========

class SerializableMixin(ABC):
"""抽象 mixin 强制实现者提供 to_dict / from_dict"""
@abstractmethod
def to_dict(self) -> Dict[str, Any]: ...
@classmethod
@abstractmethod
def from_dict(cls, data: Dict[str, Any]) -> "SerializableMixin": ...
def to_json(self) -> str:
import json; return json.dumps(self.to_dict(), ensure_ascii=False)
@classmethod
def from_json(cls, raw: str) -> "SerializableMixin":
return cls.from_dict(json.loads(raw))

class Product(SerializableMixin):
def __init__(self, pid: int, name: str, price: float) -> None:
self.pid, self.name, self.price = pid, name, price
def to_dict(self) -> Dict[str, Any]:
return {"id": self.pid, "name": self.name, "price": self.price}
@classmethod
def from_dict(cls, data: Dict[str, Any]) -> "Product":
return cls(data["id"], data["name"], data["price"])


# ========== 3. **kwargs 协作式 super() 模式 ==========

class BaseMixin:
"""所有 Mixin 的基类，**kwargs 实现协作链"""
def __init__(self, **kwargs: Any) -> None:
super().__init__(**kwargs)

class TimestampMixin(BaseMixin):
def __init__(self, **kwargs: Any) -> None:
self.created = kwargs.pop("created", None)
self.updated = kwargs.pop("updated", None)
super().__init__(**kwargs)

class VersionMixin(BaseMixin):
def __init__(self, **kwargs: Any) -> None:
self.version = kwargs.pop("version", 1)
super().__init__(**kwargs)

class ValidateMixin(BaseMixin):
def validate(self) -> bool:
return True

class SaveMixin(BaseMixin):
def save(self) -> None:
if hasattr(self, "validate") and not self.validate():
raise ValueError("验证失败")
print(f"保存 {self.__class__.__name__}")


# ========== 4. 多重组合与 MRO ==========

class Doc(TimestampMixin, VersionMixin, ValidateMixin, SaveMixin):
"""组合多个 Mixin，super().__init__ 触发 MRO 链"""
def __init__(self, title: str, **kwargs: Any) -> None:
self.title = title
super().__init__(**kwargs)
def validate(self) -> bool:
return bool(self.title)

d = Doc("标题", created="2024-01-01", version=3)
print(Doc.__mro__); d.save()
# 原则：Mixin 命名后缀；**kwargs；统一 BaseMixin；正交避免依赖