爲什麼.freeze和.dup SomeGem :: VERSION？

Question

我一邊讀https://github.com/thoughtbot/high_voltage源代碼，我在寶石規格文件中找到：

Gem::Specification.new do |s| 
    s.name  = 'high_voltage' 
    s.version  = HighVoltage::VERSION.dup 

和lib/high_voltage/version.rb文件：

module HighVoltage 
    VERSION = "2.2.1".freeze 
end 

什麼是這樣做的好處呢？

Answer 1

根據http://alexpeattie.com/blog/defining-versions-in-ruby-gems/，它使字符串不可變，因此不會意外更改。