类中通用项的通用集合？

Question

I'm trying to create a class that accepts two generic types (IQueue, IItem) for example:

public class Coordinator<T,K>
    where T : IQueue<K>
    where K : IItem
{
    private T<K> collection = new T<K>();
}

Where:

public interface IQueue<T> where T : IItem
{
}

public class MyQueue<T> : IQueue<T>
    where T : IItem
{
}

But the compiler does not like:

private T<K> collection = new T<K>();

Is this at all possible?

Thanks!

Answer 1

I think you need to do the following:

public interface IQueue<T> where T : IItem
{
}

public class MyQueue<T> : IQueue<T>
    where T : IItem
{
}

Because you are saying: The coordinator gets an IQueue, but you are trying to construct a MyQueue with more specific information.

Using the already discussed Activator , you can do this without compiler errors:

class Coordinator <T,K>
    where T : IQueue<K>
    where K : IItem
{
    private T collection = (T)Activator.CreateInstance(typeof(T));
}

Answer 2

I think you might have expected that in "where T : IQueue where K : IItem" there was a sequence, however it actually needs to be explicity defined now . It would be a nice feature if this did work in the future though. Intuitively what you ask makes sense to me.

here's a suggested way to approach it.

public class Coordinator<T> where T : IQueue<T>, new()
{
    private T collection = new T();  
}
public interface IQueue<T>{}
public interface IItem{}