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I'm working on a small iOS App and got stuck with creating a pattern using NSRegularExpression class. I need a pattern that I can use to look for and match a special word and replace it later but I need to exclude this word from match in case it has already been replaced by this match. So if user processes given text several times the replacement goes only once.

Example:

I need to find and replace all "yes" in any given text with "probably yes". But I need to exclude replacement of "yes" in "probably yes" in case user processes text one more time so it won't look like "probably probably yes"

NSRegularExpression *regexYesReplace = [NSRegularExpression regularExpressionWithPattern:@"some pattern" options:0 error:&error];
NSString *replacementStringYesReplace = @"probably yes";
replacedText = [regexYesReplace stringByReplacingMatchesInString:afterText options:options range:range withTemplate:replacementStringYesReplace];

I tried to implement pattern from this question and fixed syntax for NSRegularExpression but it didn't work out.

Regex replace text but exclude when text is between specific tag

May be someone had the same problem. Thanks in advance

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Mike
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  • Simple solution: Generate a random placeholder that is not part of the string (e.g. `!F4E67O!`, generate a new one until it's not included). Replace all `probably yes` with the placeholder, then all `yes` and placeholders with `probably yes`. – Manfred Radlwimmer May 21 '16 at 08:26

1 Answers1

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You can use negative look-behind

(?<!probably )yes

Regex Demo

rock321987
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