import Foundation
let pattern = #"(?m)^(black\n{\n.*\n\s*value\s+)\d+"#
let regex = try! NSRegularExpression(pattern: pattern)
let testString = #"""
black
{
part cone;
value 20;
}
yellow
{
part wing;
value 30;
}
"""#
let stringRange = NSRange(location: 0, length: testString.utf16.count)
let substitutionString = #"\g<1>30"#
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