import Foundation
let pattern = #"[^b]:[^,]*,?"#
let regex = try! NSRegularExpression(pattern: pattern, options: .anchorsMatchLines)
let testString = ##"a:ABC,b:SDSD,c:213123#a:SDS,b:UIOU,c:89797#a:TYRQQQW,b:UIOUIOYYO,c:546654 a:DFSS,b:TYRTTN,c:12323#a:HJH,b:YTUUUTYUTYT,c:67890 a:TYY,b:OPIUIU,c:86768"##
let stringRange = NSRange(location: 0, length: testString.utf16.count)
let substitutionString = #""#
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