import Foundation
// WARNING: You included a flag that Swift doesn't support: u
//          When this flag is set, it makes the pattern and subject strings to be treated as unicode.
//          Swift already treats the pattern and subject strings as unicode by default, so including this flag is redundant.
let pattern = #"\bона\b"#
let regex = try! NSRegularExpression(pattern: pattern)
let testString = #"""
йсчфкесч ешкчфкешчг она
она йсчфкесч ешкчфкешчг она.
йсчфкесч ешкчфкешчг она .
йсчфкесч ешкчфкешчг анона.
"""#
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