Ruby从内部类访问常量 [英] Ruby accessing constants from inner-class

问题描述

我有一个类似的嵌套类：

I have a nested class like so:

class Mammal
    H = "Mammal"

    class Human
        H = "Human"
    end

end

我想制作一个人类对象，并在访问人类常数之后，像这样：

And I want to make an Human object and after access the Human's constant, like so:

human = Mammal::Human.new # makes an object successfully

puts human::H             # does not work **
puts Mammal::Human::H     # works ["Human"]
puts Mammal::H            # works ["Mammal"]

**。但它不起作用（ ..不是类/模块[TypeError]）。我在做什么错？

**.. but it won't work ("..is not a class/module [TypeError]"). What am i doing wrong?

推荐答案

我在做什么错了？

What am I doing wrong?

您正在尝试从错误的上下文引用常量。常量是在类对象中定义的，而不是在实例中定义的。可行：

You're trying to refer a constant from a wrong context. Constants are defined in class objects, not in instances. This works:

human = Mammal::Human.new
human.class.const_get(:H) # => "Human"

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