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

问题描述

Ruby 常量的真正含义是什么?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 所指的内容.

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

还是说 Ruby 常量只是一个指示，没有任何强制执行?

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

推荐答案

没错，constants 就像 ruby​​ 中的 variables，但是如果你改变了你会得到一个警告他们.

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

此外，仅变量有一个区别:即使常量是在另一个类或模块中定义的，您也可以访问常量，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 Constants::PI 访问 PI，而 Constants::other 将不起作用.

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

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