Set maximum characters (to one) in a NSTextfield in Swift

Question

How do i set the maximum amount of characters in multiple NSTextfields (OSX cocoa app, NOT iOS) to one in Swift?

Please explain how to do it, because I'm a complete newbie when it comes to OSX app development and therefore I don't understand short answers like "Use NSFormatter", because I have no idea what it is and how to implement it. Like Examples

Answer 1

You don't need to limit the characters a user will enter just only look at the first character entered. In fact, it is probably better since you will always have to handle possible user errors. If you want to you can issue an alert that they entered too many by getting the characters.count. You might want an alert if they don't answer at all. The code below will work as is if you set up a storyboard with 1 NSTextField and one button and connect them. If you have more than one textfield, i.e. like a multiple choice test, just set up all the text fields the same way.

import Cocoa

class ViewController: NSViewController {

    @IBOutlet weak var firstLetter: NSTextField!

Add as many text fields as you need:

@IBOutlet weak var secondLetter: NSTextField!

@IBOutlet weak var thirdLetter: NSTextField!

etc.

    @IBAction func button(sender: AnyObject) {

        var firstEntry = firstLetter!.stringValue

        var index1 =  firstEntry.startIndex


        if firstEntry.characters.count > 1 {

            runMyAlert("Bad USER! ONLY ONE Character!")
        }

        if firstEntry == "" {  //left it blank

            runMyAlert("You need to enter at least one character!")
            exit(0) //or you'll crash on next line
        }

        var nameLetter1:Character = firstEntry[index1]

        print( "First Letter == \(nameLetter1) ")

    }
    override func viewDidLoad() {
        super.viewDidLoad()

        // Do any additional setup after loading the view.
    }

    override var representedObject: AnyObject? {
        didSet {
        // Update the view, if already loaded.
        }
    }

    func runMyAlert( alertMessage: String){

        var myWindow = NSWindow.self
        let alert = NSAlert()
        alert.messageText = "ERROR ERROR ERROR"
        alert.addButtonWithTitle("OK")
        alert.informativeText = alertMessage
        alert.runModal()
    }
}