类型“TNestedInterface”必须可转换为“INestedInterfaceTest”才能将其用作参数“TNe

本文关键字：参数 TNe INestedInterfaceTest TNestedInterface 可转换 类型 | 更新日期: 2023-09-27 18:34:13

public interface INestedInterfaceTest<TChildType>
    where TChildType : INestedInterfaceTest<TChildType>
{
     List<TChildType> children { get; set; }
}
public abstract class NestedInterfaceTest : INestedInterfaceTest<NestedInterfaceTest>
{
    public List<NestedInterfaceTest> children { get; set; }
    public TNestedInterface GetNestedInterface<TNestedInterface>()
        where TNestedInterface : NestedInterfaceTest, new()
    {
        return GateWay<TNestedInterface>.GetNestedInterface();
    }
}
public class GateWay<TNestedInterface>
    where TNestedInterface : class, INestedInterfaceTest<TNestedInterface>, new()
{
    public static TNestedInterface GetNestedInterface()
    {
        return new TNestedInterface();
    }
}

抽象类中的 GetNestedInterface 方法出了问题。错误消息是：类型"TNestedInterface"必须可转换为"INestedInterfaceTest"，才能将其用作泛型类"GateWay"中的参数"TNestedInterface"。

但是...，我的抽象类NestedInterfaceTest实现了INestedInterfaceTest接口。我在这里错过了什么？

以下内容确实有效，无需递归接口实现：

public interface INestedInterfaceTest
{
}
public abstract class NestedInterfaceTest : INestedInterfaceTest
{
    public List<NestedInterfaceTest> children { get; set; }
    public TNestedInterface GetNestedInterface<TNestedInterface>()
        where TNestedInterface : NestedInterfaceTest, new()
    {
        return GateWay<TNestedInterface>.GetNestedInterface();
    }
}
public class GateWay<TNestedInterface>
    where TNestedInterface : class, INestedInterfaceTest, new()
{
    public static TNestedInterface GetNestedInterface()
    {
        return new TNestedInterface();
    }
}

似乎在递归实现中出错了。

类型“TNestedInterface”必须可转换为“INestedInterfaceTest”才能将其用作参数“TNe

您缺少对GetNestedInterface<>()的通用约束。 将其更改为：

public TNestedInterface GetNestedInterface<TNestedInterface>()
    where TNestedInterface : 
        NestedInterfaceTest, 
        INestedInterfaceTest<TNestedInterface>, // new
        new()
{
    return GateWay<TNestedInterface>.GetNestedInterface();
}

请注意，第二个约束是新的。

NestedInterfaceTest实现了INestedInterfaceTest<NestedInterfaceTest>，GetNestedInterface中对TNestedInterface的要求是它也应该实现INestedInterfaceTest<TNestedInterface>。

如果我创建一个不重新实现 INestedInterfaceTest<> 接口的 NestedInterfaceTest 子类，则不会满足该约束：

//does not implement INestedInterfaceTest<Derived>
class Derived : NestedInterfaceTest {}
class Derived2 : NestedInterfaceTest {}
Derived d = new Derived();
// breaks because GateWay<Derived2> cannot be constructed
d.GetNestedInterface<Derived2>();

我看到的最简单的解决方法，可能不适合您的对象模型是使用以下方法重新定义GateWay类的约束：

public class GateWay<TNestedInterface>
  where TNestedInterface : class, INestedInterfaceTest<NestedInterfaceTest>, new()
这样，从 NestedInterfaceTest

继承的任何类都将满足约束，而无需重新实现接口，因为 NestedInterfaceTest 满足了它。这样做可能更方便：

public class GateWay<TNestedInterface>
  where TNestedInterface : class, NestedInterfaceTest, new()

无论如何，即使你设法让它工作，它仍然令人困惑，无论是对于类的消费者还是对于（最终的）维护者。此外，您几乎永远无法确定某些误用

是不可能的
我想

我解决了自己的问题。请查看代码并让我知道您的想法：

public interface INestedInterfaceTest<TChildType>
    where TChildType : INestedInterfaceTest<TChildType>
{
    List<TChildType> children { get; set; }
}
public abstract class NestedInterfaceTest<TChildNestedInterface> : INestedInterfaceTest<TChildNestedInterface>
    where TChildNestedInterface : INestedInterfaceTest<TChildNestedInterface>
{
    public List<TChildNestedInterface> children { get; set; }
    public virtual TNestedInterface GetNestedInterface<TNestedInterface>()
        where TNestedInterface : NestedInterfaceTest<TChildNestedInterface>, INestedInterfaceTest<TNestedInterface>, new()
    {
        return GateWay<TNestedInterface>.GetNestedInterface();
    }
}
public class GateWay<TNestedInterface>
    where TNestedInterface : class, INestedInterfaceTest<TNestedInterface>, new()
{
    public static TNestedInterface GetNestedInterface()
    {
        List<TNestedInterface> nestedChildren = new List<TNestedInterface>();
        return new TNestedInterface
            {
                children = nestedChildren
            };
    }
}
public class NestedClass : NestedInterfaceTest<NestedClass>
{
    public NestedClass GetNestedClass()
    {
        return GetNestedInterface<NestedClass>();
    }
}

这做得很好，它可以防止界面"泄漏"。

相关文章：