How do I escape special characters in an NSString using RegexKitLite?

Question

I'm constructing a regular expression that uses strings input by the user but the strings might contain special characters such as . \ or * and I want those to be treated as literals and not interpreted by their special meanings in the regex. I've tried this:

NSString *word = [input stringByReplacingOccurrencesOfRegex:@"(\\P{L})" withString:@"\\$1"];

but the non letter characters are converted to '$1' instead of being prefixed with a backslash. I've tried one and three backslashes in the second term but those give me an 'Unknown escape sequence' warning in XCode. How can I print a backslash without RegexKitLite thinking that I'm escaping the dollar sign?

Answer 1

Write the expression as you normally would and then replace each single backslash with two. Thus

\. 

becomes

\\. 

and

\\ 

becomes

\\\\