工厂方法模式

工厂方法模式

定义一个用于创建对象的接口，让子类决定实例化哪一个类
类创建型模式 工厂父类负责定义创建产品对象的公共接口，工厂子类负责生成具体的产品对象

模式结构图

Product：定义产品的接口
ConcreteProduct:实现抽象产品接口
Factory：抽象工厂 声明一个工厂方法
ConcreteFactory：返回一个具体产品类的实例

示例：日志记录器

//Logger

    interface Logger
    {
        void WriteLog();
    }

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//FileLogger

    class FileLogger : Logger
    {
        public void WriteLog()
        {
            Console.WriteLine("File");
        }
    }

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//DataBaseLogger

    class DataBaseLogger : Logger
    {
        public void WriteLog()
        {
            Console.WriteLine("DataBase");
        }
    }

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//LoggerFactory

    interface LoggerFactory
    {
        //工厂方法的重载
        Logger CreateLogger();

        Logger CreateLogger(string args);


        Logger CreateLogger(object obj);
    }
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//DatabaseLoggerFactory

    class DatabaseLoggerFactory : LoggerFactory
    {
        public Logger CreateLogger()
        {
            //连接数据库 代码省略
            Logger logger = new DataBaseLogger();
            //初始化日志记录器 代码省略
            return logger;
        }

        public Logger CreateLogger(string args)
        {
            throw new NotImplementedException();
        }

        public Logger CreateLogger(object obj)
        {
            throw new NotImplementedException();
        }
    }

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//FileLoggerFactory

    class FileLoggerFactory : LoggerFactory
    {
        public Logger CreateLogger()
        {
            Logger logger = new FileLogger();
            //创建文件 代码省略
            return logger;
        }

        public Logger CreateLogger(string args)
        {
            throw new NotImplementedException();
        }

        public Logger CreateLogger(object obj)
        {
            throw new NotImplementedException();
        }
    }

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//client

            LoggerFactory factory;
            Logger logger;
            //读取配置文件
            string factoryType = ConfigurationManager.AppSettings["factory"];

            //反射生成对象
            factory = (LoggerFactory)Assembly.Load("FactoryMethod").CreateInstance(factoryType);
            logger = factory.CreateLogger();
            logger.WriteLog();
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