import Foundation
let pattern = #"\[b\](?!\w*.\[\/b\])"#
let regex = try! NSRegularExpression(pattern: pattern, options: .anchorsMatchLines)
let testString = #"""
By purely mathematical reasoning it is possible [b]to demonstrate ([i]or[/i] [b]prove) a theorem which...
[b]There is little point ([i]or[/i] [b]sense) in listing all of the known amino acids.
Much of the gravel is used [b]"as is" ([i]соl.[/i]) for building roads.
Tuberculin test [b]is of doubtful value in the elderly since its interpretation is very difficult.
[b](As) viewed from the top ([i]or[/i] [b]from above) the insect's abdomen swings to the top as if it were a rudder.
"""#
let stringRange = NSRange(location: 0, length: testString.utf16.count)
let matches = regex.matches(in: testString, range: stringRange)
var result: [[String]] = []
for match in matches {
var groups: [String] = []
for rangeIndex in 1 ..< match.numberOfRanges {
let nsRange = match.range(at: rangeIndex)
guard !NSEqualRanges(nsRange, NSMakeRange(NSNotFound, 0)) else { continue }
let string = (testString as NSString).substring(with: nsRange)
groups.append(string)
}
if !groups.isEmpty {
result.append(groups)
}
}
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