您需要使用另一个反斜杠来转义反斜杠.所以如果你想用 "\:" 替换 ":" 你需要用 "\\:" 替换.

You need to escape backslashes with another backslash. So if you want to replace ":" with "\:"you need to replace with "\\:".

let backslashString = string.replacingOccurrences(of: ":", with: "\\:")