import Foundation
let pattern = #"^[\D]*(?P<from_day>(0?[1-9])|([12][0-9])|3[01])[\.\-\s,■]+(?P<from_month>(0?[1-9])|(1[0-2]))[\.\-\s,■]*(?P<until_day>(0?[1-9])|[12][0-9]|3[01])[\.\-\s,■]+(?P<until_month>(0?[1-9])|1[012])[\D]*$|(?:.*)"#
let regex = try! NSRegularExpression(pattern: pattern, options: .anchorsMatchLines)
let testString = #"""
28.11 16.12
"13.01 23,09"
01.08.-31.12
"01.01,-51.12"
01.08.-31.12.
01.08.-31.12.
01.01.-31.12.
01.08.-31.12.
01.01.-31.12.
"01,01.-31,12."
01083112
1.02 - 4.3
"""#
let stringRange = NSRange(location: 0, length: testString.utf16.count)
let substitutionString = #"\g<from_day>.\g<from_month>-\g<until_day>.\g<until_month>"#
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