您可以将替换作为散列提供。键要匹配模式（必须是字符串），值要替换：

>> "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*

你可以在一个块中使用Ruby的gsub()函数，例如。

puts 'red, blue'.gsub(/\b(?:red|blue)\b/) { |word| word == "red" ? "blue" : "red" }
=> "blue, red"

这里的想法是全局搜索red或blue。然后将匹配传递给一个块（在其他编程语言中通常称为回调或lambda函数），该块将red交换为blue，反之亦然。

像这样使用临时占位符

str = "red, blue"
placeholder = "###TEMP_PLACEHOLDER###"

result = str.gsub("red", placeholder).gsub("blue", "red").gsub(placeholder, "blue")

puts result