Convert 2 similar computed properties to use 1 reusable function in Swift? - swift

Question

I have 2 similar computed properties like x & y
struct Window {
let defaults = UserDefaults.standard
var x: String {
get {
let x = defaults.string(forKey: "x")
return x ?? "3"
}
set {
defaults.set(newValue, forKey: "x")
}
}
var y: String {
get {
let y = defaults.string(forKey: "y")
return y ?? "10"
}
set {
defaults.set(newValue, forKey: "y")
}
}
}
And as x & y are doing the same thing, I want it to make it as a reusable function taking 2 different parameters, the forKey name like "x" & "y" & defaultValue like "2" or "3" in the above example.
I'm new to Swift & can't seem to figure it out if its possible or too easy. How should I do it?

Answer 1

struct Window {
let defaults = UserDefaults.standard
var x: String {
get {
return getValue(for:"x", defaultValue: "3")
}
set {
set(value: newValue, for:"x")
}
}
var y: String {
get {
return getValue(for:"y", defaultValue: "10")
}
set {
set(value: newValue, for:"y")
}
}
func getValue(for key:String, defaultValue:String) -> String {
let value = defaults.string(forKey: key)
return value ?? defaultValue
}
func set(value:String, for key:String) {
defaults.set(value, forKey:key)
}
}

Answer 2

Note that this approach used in your question and posted answers would not work for multiple objects. What you should do is extend UserDefaults and add a static property nested in a Window struct as follow:
extension UserDefaults {
struct Window { }
}
extension UserDefaults.Window {
static var x: CGFloat {
get {
return CGFloat(UserDefaults.standard.object(forKey: "Window.x") as? Double ?? 2.0)
}
set {
UserDefaults.standard.set(Double(newValue), forKey: "Window.x")
}
}
static var y: CGFloat {
get {
return CGFloat(UserDefaults.standard.object(forKey: "Window.y") as? Double ?? 3.0)
}
set {
UserDefaults.standard.set(Double(newValue), forKey: "Window.y")
}
}
}
Playground testing
UserDefaults.Window.x // 2 default value
UserDefaults.Window.x = 10
UserDefaults.Window.x // 10
A better approach (as already mentioned by #Sulthan in comments) would be merging x and y properties in a point (CGPoint) property
extension UserDefaults.Window {
static var point: CGPoint {
get {
guard let data = UserDefaults.standard.data(forKey: "Window.point") else { return CGPoint(x: 2, y: 3) }
return (NSKeyedUnarchiver.unarchiveObject(with: data) as? NSValue)?.cgPointValue ?? CGPoint(x: 2, y: 3)
}
set {
UserDefaults.standard.set(NSKeyedArchiver.archivedData(withRootObject: newValue), forKey: "Window.point")
}
}
}
Playground testing
UserDefaults.Window.point // {x 2 y 3} default value
UserDefaults.Window.point = .zero
UserDefaults.Window.point // {x 0 y 0}