如何为泛型方法编写接口

Question

我有 PlayersCollection 类，我想在 IWorldCollection 中连接它。 问题在于在界面中编写声明导致我出现此错误：

Assets/Scripts/Arcane/api/Collections/ItemsCollection.cs(17,22): error CS0425:
The constraints for type parameter `T' of method
`Arcane.api.ItemsCollection.Get<T>(int)
must match the constraints for type parameter `T' of
interface method `Arcane.api.IWorldCollection.Get<T>(int)'.
Consider using an explicit interface implementation instead

这是我的班级和我的界面。如何编写带有类约束的泛型方法实现？

public class PlayersCollection : IWorldCollection
{

    public Dictionary<Type, object> Collection;

    public PlayersCollection()
    {
        Collection = new Dictionary<Type, object>();
    }

    public T Get<T>(int id) where T: PlayerModel
    {
       var t = typeof(T);
       if (!Collection.ContainsKey(t)) return null;
       var dict = Collection[t] as Dictionary<int, T>;
       if (!dict.ContainsKey(id)) return null;
       return (T)dict[id];
    }
  }
}


public interface IWorldCollection
{
    T Get<T>(int id) where T : class;// Work when I change "class" to "PlayerModel".
}

非常感谢您的帮助:)

Answer 1

在我看来，通过将泛型类型参数提升到类/接口级别，以下内容将满足要求：

public class PlayersCollection<T> : IWorldCollection<T> where T : PlayerModel
{

    public Dictionary<Type, T> Collection;

    public PlayersCollection()
    {
        Collection = new Dictionary<Type, T>();
    }

    public T Get(int id)
    {
       var t = typeof(T);
       if (!Collection.ContainsKey(t)) return null;
       var dict = Collection[t] as Dictionary<int, T>;
       if (!dict.ContainsKey(id)) return null;
       return (T)dict[id];
    }
  }

public interface IWorldCollection<T> where T : class
{
    T Get(int id);
}

如果我遗漏了要求中的某些内容，请告诉我。

Answer 2

我不确定你为什么需要这个界面，但也许这会有所帮助：

public class PlayersCollection<T> : IWorldCollection<T> where T:PlayerModel
{

public Dictionary<Type, object> Collection;

public PlayersCollection()
{
    Collection = new Dictionary<Type, object>();
}

public T Get(int id)
{
    ...
}
}



public interface IWorldCollection<T> where T:class
{
    T Get(int id);
}

Answer 3

试试这个：

public class PlayersCollection : IWorldCollection<PlayerModel>
{

    public Dictionary<Type, object> Collection;

    public PlayersCollection()
    {
        Collection = new Dictionary<Type, object>();
    }

    public PlayerModel Get<PlayerModel>(int id)
    {
        ///
    }
  }
}


public interface IWorldCollection<T>
{
    T Get<T>(int id);
}

在您的情况下，在实现您的接口的类中，您为您的类添加了更多条件：

• 界面中的where T : class
• where T: PlayerModel在课堂上

如果出于某种原因，您需要在接口中添加约束，则需要添加接口或基类，它们将被放置到接口声明中，并且您必须在 @ 中从它派生987654324@类，像这样：

public abstract class Model
{
}

public class PlayerModel : Model
{
}

public interface IWorldCollection<T> where T : Model
{
    T Get<T>(int id);
}

public class PlayersCollection : IWorldCollection<PlayerModel>
{
    ///

    public PlayerModel Get<PlayerModel>(int id)
    {
        ///
    }
  }
}