Question

我有以下界面：

public interface INotificationHandler<T>
{
    Task<T> Handle(string msg);
}

有几个类很乐意实现它：

public class FooHandler : INotificationHandler<Foo>
{
    public Task<Foo> Handle(string msg) { return Task.FromResult<Foo>(new Foo()); }
}

public class BarHandler : INotificationHandler<Bar>
{
    public Task<Bar> Handle(string msg) { return Task.FromResult<Bar>(new Bar()); }
}

我想在集合中保留一组INotificationHandler实例，当我收到消息＆＃34; foo＆＃34;时，请使用FooHandler，＆＃34; bar＆＃34;获得BarHandler等......

var notificationHandlers = new Dictionary<string, INotificationHandler<object>>();
notificationHandlers["foo"] = new FooHandler();
notificationHandlers["bar"] = new BarHandler();
...
public void MessageReceived(string type, string msg)
{
    INotificationHandler<object> handler = notificationHandlers[type];
    handler.Notify(msg).ContinueWith((result) => /* do stuff with a plain object */)
}

但是这无法编译，因为我的通用没有通用的基类型，这是设计的。任何对象都应该能够从MessageReceived中的INotificationHandler返回。

无法将FooHandler类型隐式转换为INotificationHandler<object>。存在显式转换（您是否错过了演员？）

我如何使用INotificationHandler<T>以便我不需要关心其具体实现的泛型类型？

Answer 1

如果您需要类型安全，可以使用以下层次结构。

public interface INotificationHandler
{
    Task<object> Handle(string msg);
}

public abstract BaseHandler<T> : INotificationHandler
{
    Task<object> INotificationHandler.Handle(string msg)
    {
        return Handle(msg);
    }

    public abstract Task<T> Handle(string msg);
}

public class FooHandler : BaseHandler<Foo>
{
    public override Task<Foo> Handle(string msg) { return Task.FromResult<Foo>(new Foo()); }
}

public class BarHandler : BaseHandler<Bar>
{
    public override Task<Bar> Handle(string msg) { return Task.FromResult<Bar>(new Bar()); }
}

var notificationHandlers = new Dictionary<string, INotificationHandler>();
notificationHandlers["foo"] = new FooHandler();
notificationHandlers["bar"] = new BarHandler();
...
public void MessageReceived(string type, string msg)
{
    INotificationHandler handler = notificationHandlers[type];
    handler.Notify(msg).ContinueWith((result) => /* do stuff with a plain object */)
}

无法在C＃中将具体类型转换为其接口的通用版本

1 个答案: