如何在Xcode中对键入到TextField中的Integer值进行排序？

Question

I've just started to do some simple programming with Swift, things like building a simple calculator and stuff like that. Now I would like to create an app that allows me to sort a bunch of integer values which the user is typing into the TextField. Down here is what I've got so far. Could you please tell me where my mistake is?

class ViewController2: UIViewController {
    @IBOutlet var randomNumbers: UITextField!
    @IBOutlet var finalResult: UITextView!

    @IBAction func SortNumbers(_ sender: UIButton) {
        let sortedNumbers = Int[randomNumbers.text]
        let sortedNubers = sortedNumbers.sort{$1>$2}
        finalResult.text = String(sortedNumbers)
    }

Answer 1

it's not the best answer you could get, but it might solves your problem:

@IBAction func sortNumbers(_ sender: UIButton) {
    let stringWithNumbers = "1 23 12 4 5 12"
    let sortedNumbers = stringWithNumbers.components(separatedBy: " ").flatMap { Int($0) }
    let sortedNubers = sortedNumbers.sorted { $0 > $1 }
    print(sortedNubers.description)
}

Answer 2

You're not converting it into an Int array properly. If we can assume that the input string is a comma-separated list with no spaces:

let sortedNumbers = randomNumbers.text.components(separatedBy: ",").map{ Int($0) ?? 0 }

components splits it into a string array using commas as a reference, and then map converts each element into an Int (and ?? 0 catches any invalid input and prevents it from being an array of optionals).

Also, for the sake of your sanity and that of anyone who might have to read your code later, avoid using nearly-identical variable names like sortedNumbers and sortedNubers . If you need to use multiple variables for the same data, make their differences more descriptive (for instance, the first one should probably be unsortedNumbers in this case).

Answer 3

Your mistake is in trying to treat a single string as if it were an array of numbers. You're missing two steps in there:

• Parsing: Take the string that the user has typed and turn it into numbers
• Formatting: Take the stored numbers and turn them back into a string to display

Lurking in that first step is the possibility that the user has not actually typed in integers. An approach that just ignores non-integer input would look like:

@IBAction func sortTextAction(_ sender: UIButton) {
  guard let text = randomNumbers.text else {
    finalResult.text = ""  // clear out - no result on empty input
    return
  }

  // Parse String -> [Int]:
  // Split into words, then turn words into Ints,
  // while discarding non-Int words
  let words = text.components(separatedBy: CharacterSet.whitespacesAndNewlines)
  let numbers = words
    .map({ Int($0) })  // String -> Int?
    .flatMap({ $0 })  // discard any nil values

  let sorted = numbers.sort()

  // Format [Int] -> String: glue the sorted Ints together with a space between each
  finalResult.text = sorted
    .map({ String(describing: $0 })  // Int -> String: turn 1 into "1"
    .joined(separator: " ")  // [String] -> String: turn [1, 2, 3] into "1 2 3"
}

}

Lurking behind both of these is localization: What one locale writes as "1,000" might be "1 000" or "1.000" elsewhere. For that, you'd pull in NumberFormatter to handle the conversions in a locale-aware way.