import Foundation
let pattern = #"((?:INV)\+(?:[^+\n]*\+){4})\d{8}"#
let regex = try! NSRegularExpression(pattern: pattern, options: .anchorsMatchLines)
let testString = #"""
UNA:+,? '
UNB+UNOC:3+000000000+000000000+20190801:1115+00001+DDMP190001'
UNH+00001+BRKE:01+00+0'
INV+ED Format 1+Brustkrebs+19880117+E000000001+20080702+++1+0'
FAL+087897044+0000000++Trägername+000000000+0+20080702++1+++J+N+N+N+N+N+++0'
INL+181095200+385762115+++0'
BEE+20080702++++0'
BAA+++J+J++++++J+++++++J++0'
BBA++++++++J++++++J+J++++++J+++++J+++J+J++++++++J+0'
BHP+J+++++J+++++J+++++0'
BLA+++J+++++++++0'
BFA++++++++++++J++0'
BSA++J+++J+J+++0'
BAT+20190801+0'
DAT+20080702++++0'
UNT+000014+00001'
UNZ+00001+00001'
"""#
let stringRange = NSRange(location: 0, length: testString.utf16.count)
let substitutionString = #"\g<1>20200101"#
let result = regex.stringByReplacingMatches(in: testString, range: stringRange, withTemplate: substitutionString)
print(result)
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Swift 5.2, please visit: https://developer.apple.com/documentation/foundation/nsregularexpression