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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?

Mike T
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1 Answers1

7

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

\.

becomes 

\\.

and 

\\

becomes 

\\\\
Matthew Frederick
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  • Thanks Matthew. Four backslashes is what is needed in this case. Don't know why I didn't try it in the first place. – Mike T Dec 05 '10 at 07:45