ruby - 如何让gsub方法只改变一次

Question

我没有很好地表达标题，因为我无法解释它，但如果我有的话，可以说我有这样的东西

puts ("red, blue").gsub("red", "blue").gsub("blue", "red")

我想让“红，蓝”变成“蓝，红”，这是彼此相反的，但是因为“红”变成“蓝”，然后“蓝”变成“红”马上又回来了，它只是不起作用。

我尝试了另一种方法，我想让“快乐”一词的所有实例都被“悲伤”替换，反之亦然

Answer 1

您可以以散列形式提供替换。匹配模式的键(必须是字符串)，值是替换:

>> "red, blue, blue, green".gsub(/red|blue/, {"red" => "blue", "blue" => "red"})
=> "blue, red, red, green"

>> "happy happy sad".gsub(/sad|happy/, {"sad" => "happy", "happy" => "sad"})
=> "sad sad happy"

---

对于更复杂的操作:

"happy happy sad red blue".gsub(/\w+/) do |m|
  case m
  when "happy" then "red"
  when "sad"   then "blue"
  when "red"   then "sad"
  when "blue"  then "happy"
  end
end
=> "red red blue sad happy"

---

https://rubyapi.org/3.3/o/string#class-String-label-Substitution+Methods