Ruby“.downcase！"和“小写"困惑 [英] Ruby ".downcase! " and "downcase" confusion

问题描述

我刚刚开始 Ruby 编程.我读过 小写和小写之间的区别！在 Ruby 中.然而我在实践中遇到了一个有趣的问题，这里是代码:

I just started Ruby programming. I had read Difference Between downcase and downcase! in Ruby. However I encounter an interesting problem in practice, here is code:

a = "lower"
a = a.downcase
print a

Compiler return: lower

但是，如果我尝试:

a = "lower"
a = a.downcase!
print a

Compiler return: nil

但是，如果a = LOWER"，两个版本的代码都返回lower"

However, both version of code returns "lower" if "a = LOWER"

推荐答案

小写！→ str 或 nil

downcase! → str or nil

将 str 的内容小写，如果未进行任何更改，则返回 nil.注意:大小写替换仅在 ASCII 区域有效.

Downcases the contents of str, returning nil if no changes were made. Note: case replacement is effective only in ASCII region.

文档:String#downcase！

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