How to replace the last occurrence of a substring in ruby?

Question

I want to replace the last occurrence of a substring in Ruby. What\'s the easiest way? For example, in abc123abc123, I want to replace the last abc

Answer 1

string = "abc123abc123"
pattern = /abc/
replacement = "ABC"

matches = string.scan(pattern).length
index = 0
string.gsub(pattern) do |match|
  index += 1
  index == matches ? replacement : match
end
#=> abc123ABC123