Restrict NSTextField to only allow numbers

Question

How do I restrict a NSTextfield to allow only numbers/integers? I\'ve found questions like this one, but they didn\'t help!

Answer 1

[Works with Swift 3.0.1]

As others suggested, subclass NumberFormatter and override isPartialStringValid method. The easiest way is to drop a NumberFormatter object under your NSTextField in xib/storyboard and update it's Custom Class. Next implementation allows only integers or blank value and plays a beep if string contains illegal characters.

class IntegerFormatter: NumberFormatter {

    override func isPartialStringValid(_ partialString: String, newEditingString newString: AutoreleasingUnsafeMutablePointer?, errorDescription error: AutoreleasingUnsafeMutablePointer?) -> Bool {

        // Allow blank value
        if partialString.numberOfCharacters() == 0  {
            return true
        }

        // Validate string if it's an int
        if partialString.isInt() {
            return true
        } else {
            NSBeep()
            return false
        }
    }
}

String's numberOfCharacters() and isInt() are methods added in an extension.

extension String {

    func isInt() -> Bool {

        if let intValue = Int(self) {

            if intValue >= 0 {
                return true
            }
        }

        return false
    }

    func numberOfCharacters() -> Int {
        return self.characters.count
    }
}