How to detect when UIView size is changed in swift ios xcode?

There's an answer here:

https://stackoverflow.com/a/27590915/5160929

Just paste this outside of a method body:

override var bounds: CGRect {
    didSet {
        // Do stuff here
    }
}

viewWillLayoutSubviews() and viewDidLayoutSubviews() will be called whenever the bounds change. In the view controller.