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"""
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工厂方法模式 (Factory Method Pattern)
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意图：定义一个用于创建对象的接口，让子类决定实例化哪个类。工厂方法使一个类的实例化延迟到其子类。
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应用场景：
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- 当一个类不知道它所必须创建的对象的类的时候
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- 当一个类希望由它的子类来指定它所创建的对象的时候
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- 当类将创建对象的职责委托给多个帮助子类中的某一个，并且你希望将哪一个帮助子类是代理者这一信息局部化的时候
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结构：
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- Product: 定义工厂方法所创建的对象的接口
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- ConcreteProduct: 实现Product接口
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- Creator: 声明工厂方法，该方法返回一个Product类型的对象
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- ConcreteCreator: 重写工厂方法以返回一个ConcreteProduct实例
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"""
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from abc import ABC, abstractmethod
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class Product(ABC):
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"""产品接口，定义所有具体产品共有的操作"""
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@abstractmethod
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def operation(self) -> str:
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"""抽象操作方法"""
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pass
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class ConcreteProductA(Product):
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"""具体产品A"""
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def operation(self) -> str:
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return "返回产品A的操作结果"
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class ConcreteProductB(Product):
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"""具体产品B"""
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def operation(self) -> str:
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return "返回产品B的操作结果"
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class ConcreteProductC(Product):
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"""具体产品C"""
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def operation(self) -> str:
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return "返回产品C的操作结果"
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class Creator(ABC):
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"""创建者抽象类，声明工厂方法"""
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@abstractmethod
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def factory_method(self) -> Product:
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"""工厂方法，返回一个产品实例"""
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pass
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def some_operation(self) -> str:
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"""业务逻辑，依赖于factory_method创建的产品对象"""
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# 调用工厂方法创建产品
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product = self.factory_method()
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# 使用产品执行操作
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result = f"创建者：使用{product.__class__.__name__}执行操作\n{product.operation()}"
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return result
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class ConcreteCreatorA(Creator):
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"""具体创建者A，创建产品A"""
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def factory_method(self) -> Product:
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return ConcreteProductA()
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class ConcreteCreatorB(Creator):
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"""具体创建者B，创建产品B"""
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def factory_method(self) -> Product:
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return ConcreteProductB()
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class ConcreteCreatorC(Creator):
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"""具体创建者C，创建产品C"""
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def factory_method(self) -> Product:
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return ConcreteProductC()
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# 扩展：参数化工厂方法
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class ParameterizedCreator:
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"""参数化的工厂类，根据参数创建不同的产品"""
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@staticmethod
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def create_product(product_type: str) -> Product:
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"""根据参数创建产品
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Args:
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product_type: 产品类型标识
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Returns:
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Product: 创建的产品实例
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Raises:
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ValueError: 当产品类型无效时
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"""
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if product_type == "A":
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return ConcreteProductA()
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elif product_type == "B":
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return ConcreteProductB()
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elif product_type == "C":
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return ConcreteProductC()
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else:
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raise ValueError(f"未知的产品类型: {product_type}")
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# 实际应用示例：文档导出器
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class DocumentExporter(ABC):
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"""文档导出器接口"""
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@abstractmethod
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def export(self, content: str) -> str:
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"""导出文档
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Args:
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content: 文档内容
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Returns:
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str: 导出结果
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"""
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pass
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class PDFExporter(DocumentExporter):
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"""PDF格式导出器"""
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def export(self, content: str) -> str:
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return f"PDF导出成功：将'{content}'转换为PDF格式"
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class WordExporter(DocumentExporter):
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"""Word格式导出器"""
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def export(self, content: str) -> str:
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return f"Word导出成功：将'{content}'转换为DOCX格式"
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class HTMLExporter(DocumentExporter):
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"""HTML格式导出器"""
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def export(self, content: str) -> str:
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return f"HTML导出成功：将'{content}'转换为HTML格式"
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class DocumentExporterCreator(ABC):
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"""文档导出器创建者抽象类"""
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@abstractmethod
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def create_exporter(self) -> DocumentExporter:
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"""创建导出器的工厂方法"""
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pass
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def export_document(self, content: str) -> str:
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"""导出文档的业务逻辑"""
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exporter = self.create_exporter()
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return exporter.export(content)
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class PDFExporterCreator(DocumentExporterCreator):
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"""PDF导出器创建者"""
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def create_exporter(self) -> DocumentExporter:
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return PDFExporter()
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class WordExporterCreator(DocumentExporterCreator):
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"""Word导出器创建者"""
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def create_exporter(self) -> DocumentExporter:
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return WordExporter()
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class HTMLExporterCreator(DocumentExporterCreator):
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"""HTML导出器创建者"""
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def create_exporter(self) -> DocumentExporter:
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return HTMLExporter()
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def main():
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"""演示工厂方法模式"""
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print("=== 工厂方法模式演示 ===")
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# 基本工厂方法模式演示
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print("\n1. 基本工厂方法模式：")
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creators = [
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ConcreteCreatorA(),
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ConcreteCreatorB(),
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ConcreteCreatorC()
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]
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for creator in creators:
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print(f"\n{creator.__class__.__name__}:")
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print(creator.some_operation())
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# 参数化工厂方法演示
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print("\n2. 参数化工厂方法：")
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try:
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for product_type in ["A", "B", "C"]:
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product = ParameterizedCreator.create_product(product_type)
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print(f"\n创建产品类型 {product_type}:")
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print(product.operation())
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# 测试错误处理
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ParameterizedCreator.create_product("D")
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except ValueError as e:
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print(f"\n异常处理测试: {e}")
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# 实际应用示例：文档导出器
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print("\n3. 实际应用示例 - 文档导出器：")
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exporters = [
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PDFExporterCreator(),
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WordExporterCreator(),
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HTMLExporterCreator()
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]
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document_content = "这是一篇测试文档内容"
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for exporter in exporters:
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print(f"\n{exporter.__class__.__name__}:")
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print(exporter.export_document(document_content))
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if __name__ == "__main__":
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main() |
