投对象的通用接口 [英] Casting an object to a generic interface

问题描述

我有以下接口：

internal interface IRelativeTo<T> where T : IObject
{
    T getRelativeTo();
    void setRelativeTo(T relativeTo);
}

和一堆类，（应该）实现它，如：

and a bunch of classes that (should) implement it, such as:

public class AdminRateShift : IObject, IRelativeTo<AdminRateShift>
{
    AdminRateShift getRelativeTo();
    void setRelativeTo(AdminRateShift shift);
}

我意识到，这三个是不一样的：

I realise that these three are not the same:

IRelativeTo<>
IRelativeTo<AdminRateShift>
IRelativeTo<IObject>

但尽管如此，我需要的方式与所有不同的类，如AdminRateShift（和FXRateShift，DetRateShift工作）应该都实现IRelativeTo。比方说，我有返回AdminRateShift为对象的功能：

but nonetheless, I need a way to work with all the different classes like AdminRateShift (and FXRateShift, DetRateShift) that should all implement IRelativeTo. Let's say I have an function which returns AdminRateShift as an Object:

IRelativeTo<IObject> = getObjectThatImplementsRelativeTo(); // returns Object

通过针对接口编程，我可以做什么，我需要，但我可以'T居然投的对象IRelativeTo这样我就可以使用它。

By programming against the interface, I can do what I need to, but I can't actually cast the Object to IRelativeTo so I can use it.

这是一个简单的例子，但我希望它会澄清什么，我试图做的。

It's a trivial example, but I hope it will clarify what I am trying to do.

推荐答案

如果我理解的问题，那么最常用的方法是申报非通用底座接口，即

If I understand the question, then the most common approach would be to declare a non-generic base-interface, i.e.

internal interface IRelativeTo
{
    object getRelativeTo(); // or maybe something else non-generic
    void setRelativeTo(object relativeTo);
}
internal interface IRelativeTo<T> : IRelativeTo
    where T : IObject
{
    new T getRelativeTo();
    new void setRelativeTo(T relativeTo);
}

另一个选择是让你在很大程度上泛型代码...即你有像

Another option is for you to code largely in generics... i.e. you have methods like

void DoSomething<T>() where T : IObject
{
    IRelativeTo<IObject> foo = // etc
}

如果在 IRelativeTo< T> ; 是一个参数 DoSomething的（），然后的一般的，你不需要自己指定泛型类型参数 - 编译器会推断出它 - 即

If the IRelativeTo<T> is an argument to DoSomething(), then usually you don't need to specify the generic type argument yourself - the compiler will infer it - i.e.

DoSomething(foo);

而不是

rather than

DoSomething<SomeType>(foo);

有这两种方法的好处。

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