How can I animate the change of the navigation bar title - swift

Question

I am looking for a way to run a custom CAAnimation on the UINavigationBar title.
More precisely, I am looking for a way to access the label which displays navigationItem.title and run animations on that.
It is certainly possible to manually create a UILabel and set the navigationBar.titleView accordingly.
This however seems to be too much effort for a hopefully simple problem. Plus, it will not work well with large titles on the UInavigationBar.

Answer 1

The title text is accessible as topItem.text. There is no way to directly access the label which is displaying this text.
So if you want to animate this label, you first have to search for it in the subview of the NavigationBar.
Then, you can apply animations on this label.
See below for an example that fades in the new title from the right.
/// Fades in the new title from the right
///
/// - Parameter newTitle: New title to display on the navigation item
func animateTitle(newTitle: String) {
// Title animation code
let titleAnimation = CATransition()
titleAnimation.duration = 0.25
titleAnimation.type = CATransitionType.push
titleAnimation.subtype = CATransitionSubtype.fromRight
titleAnimation.timingFunction = CAMediaTimingFunction.init(name: CAMediaTimingFunctionName.easeInEaseOut)
// Find the Label which contains the topitem title
if let subviews = navigationController?.navigationBar.subviews {
for navigationItem in subviews {
for itemSubView in navigationItem.subviews {
if let largeLabel = itemSubView as? UILabel {
largeLabel.layer.add(titleAnimation, forKey: "changeTitle")
}
}
}
}
navigationItem.title = newTitle
}