Ruby常数是什么意思？ [英] What does Ruby constant mean?

问题描述

Ruby常数真正意味着什么？以下代码未显示任何常量属性。警告在那里，但我仍然可以更改A的含义。

What does Ruby constants really mean? The following code doesn't show any 'constant' attribute. The warning is there, but I still get to change what A refers to.

A = 1
puts A # => 1
A = 2  # warning: already initialized constant A
puts A # => 2

还是Ruby常数只是没有任何强制性的指示？

Or is Ruby constants are just an indication without any enforcement?

推荐答案

是的，常量就像红宝石中的变量一样，但是如果您进行更改，则会收到警告

That's right, constants are just like variables in ruby, but you get a warning if you change them.

此外，纯变量也有一个区别：即使常量是在另一个类或模块中定义的，也可以访问常量，例如给出以下代码段：

Also, there's one difference with mere variables: You can access constants even if they are defined inside another class or module, for example given this snippet:

module Constants
  PI = 3,1415
  other = "variable"
end

您可以通过常量来达到 PI :: PI ，而 Constants :: other 不起作用。

You can reach PI doing Constants::PI while Constants::other will not work.

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