Property getters and setters

compiler-warnings, getter-setter, properties, swift

Solution

Setters and Getters apply to `computed properties`; such properties do not have storage in the instance - the value from the getter is meant to be computed from other instance properties. In your case, there is no `x` to be assigned.

Explicitly: "How can I do this without explicit backing ivars". You can't - you'll need something to backup the computed property. Try this:

class Point {
  private var _x: Int = 0             // _x -> backingX
  var x: Int {
    set { _x = 2 * newValue }
    get { return _x / 2 }
  }
}

Specifically, in the Swift REPL:

 15> var pt = Point()
pt: Point = {
  _x = 0
}
 16> pt.x = 10
 17> pt
$R3: Point = {
  _x = 20
}
 18> pt.x
$R4: Int = 10

Problem

With this simple class I am getting the compiler warning Attempting to modify/access `x` within its own setter/getter and when I use it like this: ``` var p: point = Point() p.x = 12 ``` I get an EXC_BAD_ACCESS. How can I do this without explicit backing ivars? ``` class Point { var x: Int { set { x = newValue * 2 //Error } get { return x / 2 //Error } } // ... } ```

Original source