Read-only and non-computed variable properties in Swift

Question

I\'m trying to figure out something with the new Apple Swift language. Let\'s say I used to do something like the following in Objective-C. I have readonly prop

Answer 1

Actually access control (which does not exist yet in Swift) is not as enforced as you may think in Objective C. People can modify your readonly variables directly, if they really want to. They just do not do it with the public interface of the class.

You can do something similar in Swift (cut&paste of your code, plus some modifications, I did not test it):

class Clock : NSObject {

    var _hours:   UInt = 0
    var _minutes: UInt = 0
    var _seconds: UInt = 0

    var hours: UInt {
    get {
      return _hours
    }
    }

    var minutes: UInt {
    get {
      return _minutes
    }
    }

    var seconds: UInt  {
    get {
      return _seconds
    }
    }

    func incrementSeconds() {

        self._seconds++

        if self._seconds == 60 {

            self._seconds = 0
            self._minutes++

            if self._minutes == 60 {

                self._minutes = 0
                self._hours++
            }
        }
    }
}

which is the same as what you have in Objective C except that the actual stored properties are visible in the public interface.

In swift you can also do something more interesting, which you can also do in Objective C, but it's probably prettier in swift (edited in the browser, I did not test it):

class Clock : NSObject {

    var hours: UInt = 0

    var minutes: UInt {
    didSet {
      hours += minutes / 60
      minutes %= 60
    }
    }

    var seconds: UInt  {
    didSet {
      minutes += seconds / 60
      seconds %= 60
    }
    }

    // you do not really need this any more
    func incrementSeconds() {
        seconds++
    }
}