我有以下界面：
public interface INotificationHandler<T>
{
Task<T> Handle(string msg);
}
还有几个类很高兴地实现它：
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“foo”时,使用FooHandler,“bar”获取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,因为我的泛型没有共同的基类型,这是设计的.应该能够从MessageReceived中的INotificationHandler返回任何对象.
Cannot implicitly convert type
FooHandlertoINotificationHandler<object>.
An explicit conversion exists (are you missing a cast?)
如何使用INotificationHandler< T>所以我不需要关心其具体实现的泛型类型？
解决方法
如果需要类型安全性,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 */)
}
