通用类型转换

Question

由于泛型问题,我遇到了一些严重的设计问题.也许有人有一些建议.

编辑:所以,我知道这通常不会完成,但我已经完全改变了我的示例代码,因为我已经意识到原始的伪代码并没有真正解释我的问题.以下代码更接近于我正在处理的真实示例.我希望我的问题能更明确.我向前道歉它有点冗长,但根据我的经验,当你试图建立一个更复杂的结构时,通常会出现泛型问题.所以:

class Program
    {
        static void Main(string[] args)
        {
            IConnector<IService> connector = ConnectorBuilderFactory.NewBuilder<IService>("someEndpoint").MakeReliable().GetConnector();
            connector.Connect();
        }
    }

    public interface IService : IConnectionMaintainable
    {
        void DoSomething();
    }

    public interface IConnectionMaintainable
    {
        DateTime GetServerTime();
    }

    public interface IConnector<T>
    {
        T Channel { get; }
        void Connect();
        void Disconnect();
    }

    public interface IConnectorBuilder<T>
    {
        IConnector<T> GetConnector();
        IConnectorBuilder<T> MakeReliable();
        // ...more connector-configuration methods
    }

    public class ChannelWatchDog<T> where T : IConnectionMaintainable
    {
        private IConnector<T> connector;

        public ChannelWatchDog(IConnector<T> connector /*various other parameters*/)
        {
            this.connector = connector;
        }

        // ...methods that use connector's Connect, Disconnect, and GetServerTime methods
    }

    public class Connector<T> : IConnector<T>
    {
        private T channel;

        public Connector(string endpoint)
        {
            // ...build channel
        }

        public T Channel
        {
            get { return channel; }
        }

        public void Connect()
        {
            // ...connect to server
        }

        public void Disconnect()
        {
            // ...disconnect from server
        }
    }

    public class ConnectorBuilder<T> : IConnectorBuilder<T>
    {
        private string endpoint;

        public ConnectorBuilder(string endpoint)
        {
            this.endpoint = endpoint;
        }

        public IConnector<T> GetConnector()
        {
            Connector<T> connector = new Connector<T>(endpoint);

            // If reliability was requested, build the ChannelWatchDog: Following line does not compile:
            // ChannelWatchDog<T> watchDog = new ChannelWatchDog<T>(connector);

            return connector;
        }

        public IConnectorBuilder<T> MakeReliable()
        {
            // save various parameters required to build the ChannelWatchDog
            return this;
        }
    }

    public static class ConnectorBuilderFactory
    {
        public static IConnectorBuilder<T> NewBuilder<T>(string endpoint)
        {
            return new ConnectorBuilder<T>(endpoint);
        }
    }

因此,首先,如果在ConnectorBuilder类中找到GetConnector方法,您将看到注释的代码行,如果取消注释则不会编译.这一行是我的问题的本质.问题可能从代码中显而易见,但我会尝试解释它,如果它不是:

1. 我有一个需要IConnector的内部类(ChannelWatchDog).但不仅仅是IConnector,IConnector,因为除了非通用的IConnector方法之外,它还需要来自IConnectionMaintainable接口的GetServerTime方法.

2. 为了简化连接器的构造,我希望使用Expression Builder模式(IConnectionBuilder接口)实现构建器.但是,我希望能够构建任何IConnector,而不仅仅是IConnector <IConnectionMaintainable>.因此,我不能以与限制它为ChannelWatchDog相同的方式约束IConnectorBuilder中的T. 缺少这个约束,我无法在调用GetConnector时构建它.将约束添加到MakeReliable方法没有帮助.

所以,基本上我发布这个问题的原因是我想做一些显然不可能的事情.我希望ChannelWatchDog和ConnectorBuilder类看起来像这样:

public class ChannelWatchDog
    {
        private IConnector<IConnectionMaintainable> connector;

        public ChannelWatchDog(IConnector<IConnectionMaintainable> connector /*various other parameters*/)
        {
            this.connector = connector;
        }

        // ...methods that use connector's Connect, Disconnect, and GetServerTime methods
    }

    public class ConnectorBuilder<T> : IConnectorBuilder<T>
    {
        private string endpoint;

        public ConnectorBuilder(string endpoint)
        {
            this.endpoint = endpoint;
        }

        public IConnector<T> GetConnector()
        {
            Connector<T> connector = new Connector<T>(endpoint);

            // If reliability was requested, build the ChannelWatchDog: Following line does not compile:
            ChannelWatchDog watchDog = new ChannelWatchDog((IConnector<IConnectionMaintainable>)connector);

            return connector;
        }

        public IConnectorBuilder<TReliable> MakeReliable<TReliable>() where TReliable : T, IConnectionMaintainable
        {
            // save various parameters required to build the ChannelWatchDog
            return (IConnectorBuilder<TReliable>)this;
        }
    }

但是对IConnector的强制转换在运行时失败了.

所以这比我原先打算的要长得多.如果你已经阅读了这么远,那么你已经得到了我的谢意:)欢迎任何想法,包括重组代码.

顺便说一句,由于我自己没有找到解决方案,我在工厂中创建了不同的ConnectorBuilders(在本例中为ReliableConnectorBuilder)和不同的工厂方法.但我不太喜欢这个解决方案.

编辑:只是澄清并重申:我不能约束IConnector和ConnectionBuilder,因为这些需要支持未实现IConnectionMaintainable接口的情况.

Answer 1

代码接口？

GenericClass<IFoo> wrapper = new GenericClass<IFoo>(new FooImplementor());
Acceptor acceptor = new Acceptor(wrapper);