无法读取一个类的实例常量？ [英] Can't read a const in a class instance?

问题描述

我感到十分诧异，当编译器抱怨这一点：

I was mildly surprised when the compiler complained about this:

public class UsefulClass
{
    public const String RatingName = @"Ratings\rating";
}

public class OtherClass
{
    public void SomeFunc()
    {
        UsefulClass useful = new UsefulClass();
        String rating = useful.RatingName;
    }
}

编译器说的静态成员不能与实例引用访问;同一个类型名限定它，而不是的

这是没有问题的，字符串等级= UsefulClass .RatingName; 工作正常。我只是好奇的想法是这背后是什么？我有一个公共的类的实例上有一个公共不变，为什么我不能获取数据这样？

This isn't a problem, String rating = UsefulClass.RatingName; works fine. I'm just curious what the thinking is behind this? I have an instance of a public class with a public constant on it, why can't I get the data this way?

推荐答案

由于常数只是没有实例成员;他们是静态绑定到各自的类型。以同样的方式使用情况下，你不能调用静态方法，你不能访问使用实例类的常量。

Because constants just aren't instance members; they're statically bound to their respective types. In the same way you can't invoke static methods using instances, you can't access class constants using instances.

如果你需要获得恒定关断的实例，不需要知道它的类型第一手的，我想你可以根据其类型与反思做到这一点。

If you need to get a constant off an instance without knowing its type first-hand, I suppose you could do it with reflection based on its type.

如果你想补充一点，不能被修改的成员但涉及的情况下，你可能想只读字段或属性来代替。

If you're trying to add a member that can't be modified but pertains to instances, you probably want read-only fields or properties instead.

这篇关于无法读取一个类的实例常量？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！