Bind properties in Swift to NSTextFields

Question

I\'m working on a unit converter written in Swift that will automatically display the updated units within the appropriate NSTextFields. For this example, if the us

Answer 1

Is it possible to have a function that will update all the other text fields other than the currently active field?

Yes. You can connect all text field to the same action.

First connect all your text fields accordingly to your view controller:

@IBOutlet weak var hourField: NSTextField!
@IBOutlet weak var minuteField: NSTextField!
@IBOutlet weak var secondField: NSTextField!

Second create a single var to represent your time interval. You can also add a setter / getter to store it automatically to USerDefaults:

var timeInterval: TimeInterval {
    get {
        return UserDefaults.standard.double(forKey: "timeInterval")
    }
    set {
        UserDefaults.standard.set(newValue, forKey: "timeInterval")
    }
}

Third create a TimeInterval extension to convert the time from seconds to hour/minute

extension TimeInterval {
    var second: Double { return self }
    var minute: Double { return self / 60 }
    var hour:   Double { return self / 3600 }
    var hourToMinute:   Double { return self * 60 }
    var hourToSecond:   Double { return self * 3600 }
    var minuteToHour:   Double { return self / 60 }
    var minuteToSecond: Double { return self * 60 }
}

Fourth create the action that will update the other text fields:

@IBAction func timeAction(sender: NSTextField) {
    // use guard to convert the field string to Double
    guard let time = Double(sender.stringValue) else { return }
    // switch the field  
    switch sender {
    case hourField:
        // convert / update secondary fields
        minuteField.stringValue = time.hourToMinute.description
        secondField.stringValue = time.hourToSecond.description
        // make it persist through launches
        timeInterval = time * 3600
    case minuteField:
        hourField.stringValue = time.minuteToHour.description
        secondField.stringValue = time.minuteToSecond.description
        timeInterval = time * 60
    default:
        hourField.stringValue = time.hour.description
        minuteField.stringValue = time.minute.description
        timeInterval = time
    }
}

Last but not least make sure you load the values next time your view will appear:

override func viewWillAppear() {
    hourField.stringValue = timeInterval.hour.description
    minuteField.stringValue = timeInterval.minute.description
    secondField.stringValue = timeInterval.second.description
}

Sample Project