I'm trying to get a web page, parse it and return a value extracted from it. I'm getting this error. I don't really understand what I'm doing wrong. I am absolutely sure that the variable pensionAge will always be available and never go away, if that's relevant.

Any tips gratefully received.

Jeremy

func getPensionAge(dob: Date, pensionAge: inout String) {

let formatter = DateFormatter()
formatter.dateFormat = "yyyy-MM-dd"
let urlString = "https://www.gov.uk/state-pension-age/y/age/"+formatter.string(from: dob)
let reportFail = "Can’t get pension age."

pensionAge = "Looking for pension age…"

guard let url = URL(string: urlString) else { pensionAge = reportFail; return }

let rq = URLRequest(url: url)
URLSession.shared.dataTask(with: rq) { data, response, error in
    guard let data = data,
          let text = String(data: data, encoding: .utf8)
    else { DispatchQueue.main.async { pensionAge = reportFail }; return }

    let range = NSRange(location: 0, length: text.count)
    let re = try! NSRegularExpression(pattern: "State Pension age on *([0-9]* [A-Za-z]* [0-9]*)")
    let matches = re.matches(in: text, range: range)
    let nsText = text as NSString
    let results = matches.map { result in
        (0..<result.numberOfRanges).map {
            result.range(at: $0).location != NSNotFound ? nsText.substring(with: result.range(at: $0)) : ""
        }
    }

    if results.count>0 {
        formatter.dateFormat = "dd MMM yyyy"
        if let date = formatter.date(from: results[0][1]) {
            let diff = Calendar.current.dateComponents([.day], from: dob, to: date)
            let ageAtPension = (Double(diff.day ?? 0) / 365.25)
            formatter.dateFormat = "dd/MM/yyyy"
            let pensionDate = formatter.string(from: date)
            let str = "State pension date is \(pensionDate), age  \(formatNumber(ageAtPension))"
            DispatchQueue.main.async { pensionAge = str }
        }
    }
}.resume()

}

I'm not sure why you're using an inout parameter here. You should probably be doing something like return a String value or a Result instead. I'm pretty sure inout params aren't a good fit for async code like this.

Perhaps something like this:

enum PensionError: Error {
    case malformedURL
    case badData
    case dateRegexFailed
    case invalidPensionDate
    case differenceError
}

func getPensionAge(dob: Date, completion: @escaping (Result<(String, Double), PensionError>) -> Void) {
    let formatter = DateFormatter()
    formatter.dateFormat = "yyyy-MM-dd"
    let urlString = "https://www.gov.uk/state-pension-age/y/age/\(formatter.string(from: dob))"

    guard let url = URL(string: urlString) else {
        completion(.failure(.malformedURL))
        return
    }

    URLSession.shared.dataTask(with: url) { (data, response, error) in
        guard let data = data,
              let text = String(data: data, encoding: .utf8)  else {
            completion(.failure(.badData))
            return
        }

        guard let rng = text.range(of: #"State Pension age on *([0-9]* [A-Za-z]* [0-9]*)"#,
                                   options: .regularExpression) else {
            completion(.failure(.dateRegexFailed))
            return
        }

        let pensionDate = String(text[rng])
            .replacingOccurrences(of: "State Pension age on", with: "")
            .trimmingCharacters(in: .whitespacesAndNewlines)

        formatter.dateFormat = "dd MMM yyyy"
        guard let dt = formatter.date(from: pensionDate) else {
            completion(.failure(.invalidPensionDate))
            return
        }

        let diff = Calendar.current.dateComponents([.day], from: dob, to: dt)
        guard let daysDiff = diff.day else {
            completion(.failure(.differenceError))
            return
        }

        let pensionAge = Double(daysDiff) / 365.25

        completion(.success((pensionDate, pensionAge)))

    }.resume()
}

And then in the code that calls getPensionAge, you would respond accordingly depending on whether the Result was a success or a failure.

I wasn't returning a value because, as I understood it, the function would return before the URL analysis had been done by the separate thread. Thanks for your code: very interesting.

Jeremy

Yeah, sorry "return a String value or a Result" wasn't exactly the correct wording; I meant return in a completion handler like I show in that code.

yeah,As it turns out, stick it in a class coforming to ObservableObject and declare pensionAge to be @Published.

lisahaley