When is view frame size set in iOS10 SDK? - autolayout

Question

For several years in Swift and ObjC I've used this technique to make a circular view:
view.layer.cornerRadius = view.frame.size.width / 2
view.clipsToBounds = true
When UILayoutConstraints in the Storyboard are fixed width / height there has been no problem putting this code in viewDidLoad, or in viewWillAppear. Built in iOS9.3SDK it runs fine in iOS10 etc.
iOS10SDK shows framesize completely different to the fixed size in the Storyboard, even up to viewWillAppear, and in viewDidLayoutSubviews etc. My options are:
1) do this in viewDidAppear (awful solution)
2) hardcode the cornerRadius (works fine, but awful)
This looks like a bug (as a fixed width/height set in Storyboard should never be changed without at least a warning in the console). Is it, or is there a different place for this code now? (screenshot of test code attached)

Answer 1

In iOS 10, I met this issue right after I started to use Xcode 8 in june, when it was beta. This solution is needed:
Put layoutIfNeeded() right before your layer modifications:
self.view.layoutIfNeeded()
view.layer.cornerRadius = view.frame.size.width / 2
view.clipsToBounds = true
OR
place the code for corner radius to viewDidLayoutSubviews() method:
override func viewDidLayoutSubviews() {
view.layer.cornerRadius = view.frame.size.width / 2
view.clipsToBounds = true
}

Answer 2

This was bugging me all day today. I had the same issue in a few points I needed the correct frame size to draw custom UI elements, or apply style to views, particularly changing the corner radius. The solution I found was creating a subclass of UIViewController with the following implementation:
class BaseViewController: UIViewController {
/**
This is a helper property and a helper method that will be called
when the frame is calculated, but will prevent the formatting code
being called more than once
*/
private var didCalculateInitialFrame = false
private func checkIfFrameWasCalculated() {
if self.didCalculateInitialFrame == false {
self.viewDidCalculateInitialFrame()
self.didCalculateInitialFrame = true
}
}
//-- This is where you will tie your helper method with the view lifecycle
override func viewDidLayoutSubviews() {
super.viewDidLayoutSubviews()
self.checkIfFrameWasCalculated()
}
/**
This is an overridable function that you will implement
in your subclasses, in case you need to use this approach
in multiple places of your app.
*/
func viewDidCalculateInitialFrame() {
}
}
This fixed all my issues with the storyboard. I hope this is helpful.

Answer 3

This is seems problem in ios10
it can be solved by overriding the controller method viewDidLayoutSubviews() or
call method layoutIfNeeded() for the view which dimension value you might need before getting its dimension.
Objective-C :[viewObject layoutIfNeeded]
Swift: viewObject.layoutIfNeeded()
if the dimension value is still not correct then use layoutIfNeeded method for the parent view of the view object.