import Foundation
let pattern = #"0*([0-9]+)"#
let regex = try! NSRegularExpression(pattern: pattern)
let testString = #"29047531,000000029047531,70098877,000000000206616,TEST_MID_a8c59c12-5ffa-43dc-81f8-0ea4e9435a4d,000000000206616,TEST_MID_a8c59c12-5ffa-43dc-81f8-0ea4e9435a4d,TEST_MID_0ae1a070-7868-4543-811f-695f298cc9af,000000000206616,TEST_MID_a8c59c12-5ffa-43dc-81f8-0ea4e9435a4d,TEST_MID_0ae1a070-7868-4543-811f-695f298cc9af,TEST_MID_e189672a-9660-42a8-805b-b4e1f7fb431b,000000000206616,TEST_MID_a8c59c12-5ffa-43dc-81f8-0ea4e9435a4d,TEST_MID_0ae1a070-7868-4543-811f-695f298cc9af,TEST_MID_e189672a-9660-42a8-805b-b4e1f7fb431b,TEST_MID_75dc1b8b-7531"#
let stringRange = NSRange(location: 0, length: testString.utf16.count)
let substitutionString = #"$1"#
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