Tel Tel - 5 months ago 13
Swift Question

Removing duplicate lines in RegEx with Swift 2

I'm trying to remove duplicate lines with regex in Xcode with Swift. Being a beginner, I'm having some difficulties to learn how to doing it. [EDITED]

Currently for using regEx, I'm trying to use this code (please note that where I'm using two backslashes, one of them it's used just as escape character for Swift strings) adapted from http://www.regular-expressions.info/duplicatelines.html:

let originalText = "Have a nice day \n\n Have a nice day"
let myPattern = "^(.*)(\\r?\\n\\1)+$"
let replacement = "\\1"


But it seems that it don't work in my implementation.

Answer

Description

I'd modify your expression to this:

(^[^\n]*$)(?:\n\1)+

Replace With: \1

Regular expression visualization

This regular expression will do the following:

  • Find duplicate lines

Note: you'll need to replace the \ with \\ and use the following flags: Multiline so that ^ and $ match at each line, and the global option so the expression continues after the first match.

Example

Live Demo

https://regex101.com/r/uJ9rS8/4

Sample text

Have a nice day
Have a nice day
fdaf
These are not the droids you are looking for
These are not the droids you are looking for
These are not the droids you are looking for

Sample Matches

Have a nice day
fdaf
These are not the droids you are looking for

Explanation

NODE                     EXPLANATION
----------------------------------------------------------------------
  (                        group and capture to \1:
----------------------------------------------------------------------
    ^                        the beginning of a "line"
----------------------------------------------------------------------
    [^\n]*                   any character except: '\n' (newline) (0
                             or more times (matching the most amount
                             possible))
----------------------------------------------------------------------
    $                        before an optional \n, and the end of a
                             "line"
----------------------------------------------------------------------
  )                        end of \1
----------------------------------------------------------------------
  (?:                      group, but do not capture (1 or more times
                           (matching the most amount possible)):
----------------------------------------------------------------------
    \n                       '\n' (newline)
----------------------------------------------------------------------
    \1                       what was matched by capture \1
----------------------------------------------------------------------
  )+                       end of grouping
----------------------------------------------------------------------
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