Open Radar

 
Summary:
UIBarButtonItem.setTitleTextAttributes() has no effect if the item has already appeared on screen.

Steps to Reproduce:
1.) put a ViewController inside a NavigationController
2.) in viewDidLoad() add a UIBarButtonItem as the navigationItem.rightBarButtonItem
3.) write a method that sets the titleTextAttributes of the rightBarButtonItem (e.g. different foregroundColor) and can be triggered while the rightBarButtonItem is visible on screen
4.) trigger the method

Expected Results:
The rightBarButtonItem's titleTextAttributes change.

Actual Results:
The rightBarButtonItem's titleTextAttributes do not change. At all.

Workaround for the bug:
Change the rightBarButtonItem's title before or after changing the titleTextAttributes.

Sample Code:

class ViewController: UIViewController {

    private var blue = true

    override func viewDidLoad() {
        super.viewDidLoad()

        title = "Test"
        view.addGestureRecognizer(UITapGestureRecognizer(target: self, action: #selector(changeBarButtonColor)))

        navigationItem.rightBarButtonItem = UIBarButtonItem(title: "GreenButton", style: .plain, target: nil, action: nil)
        navigationItem.rightBarButtonItem?.setTitleTextAttributes(titleTextAttributes(color: .green), for: .normal)
    }

    @objc
    private func changeBarButtonColor() {

        navigationItem.rightBarButtonItem?.setTitleTextAttributes(titleTextAttributes(color: blue ? .blue : .green), for: .normal)

        // include this line and it works again:
        // navigationItem.rightBarButtonItem?.title = blue ? "BlueButton" : "GreenButton"

        blue = !blue
    }

    private func titleTextAttributes(color: UIColor) -> [NSAttributedStringKey: Any] {
        return [
            .foregroundColor: color
        ]
    }
}