Protocol-Oriented Programming Extension variable init twice - swift

Question

Here is the situation. I have a protocol, and extension of it.
protocol CustomViewAddable {
var aView: UIView { get }
var bView: UIView { get }
func setupCustomView()
}
extension CustomViewAddable where Self: UIViewController {
var aView: UIView {
let _aView = UIView()
_aView.frame = self.view.bounds
_aView.backgroundColor = .grey
// this is for me to observe how many times this aView init.
print("aView: \(_aView)")
return _aView
}
var bView: UIView {
let _bView = UIView(frame: CGRect(x: 30, y: 30, width: 30, height: 30))
_bView.backgroundColor = .yellow
return _bView
}
func setupCustomView() {
view.addSubview(aView);
aView.addSubview(bView);
}
}
And I make a ViewController to conform this protocol then I add this custom 'aView' to my ViewController's view.
class MyVC: UIViewController, CustomViewAddable {
override func viewDidLoad() {
super.viewDidLoad()
setupCustomView()
}
}
I run it. In my console log it prints twice of init and I trying to do something in my custom 'aView' and it failed. (The code I paste above that I simplified so that it'll be very easy to show my intension)
Could anybody to explain why or make a fix to it that I'll be very appreciated.

Answer 1

Because your var aView: UIView is computed variable not store variable,
So every time you call aView, it will create a new UIView,
You can use Associated Objects in NSObject here is some tutorials:
swift-objc-runtime
associated-objects
Hope this may help.

Answer 2

Basically in the way you implemented the setupCustomView method nothing should work because as mentioned in another response you're using a computed property, so this implies that every time you access the property it's created again.
You don't need to use associated-objects or something like that to achieve what you want, you only need to keep the reference of the aView at the beginning avoiding calling it again, in this way:
func setupCustomView() {
let tView = aView // only is computed once
view.addSubview(tView)
tView.addSubview(bView)
}
I hope this help you.