iOS Programming: The Big Nerd Ranch Guide, 7th Edition

Animating a Button

Let’s add one final animation touch to the application. When the current mood is changed, also animate the add mood button’s background color. You will use the same property animator technique that you used above.

Modify the property observer for currentMood to animate the button’s background color.

Listing 19.9  Animating the button’s background color (MoodSelectionViewController.swift)

var currentMood: Mood? {
    didSet {
        guard let currentMood = currentMood else {
            addMoodButton?.setTitle(nil, for: .normal)
            addMoodButton?.backgroundColor = nil
            return
        }

        addMoodButton?.setTitle("I'm \(currentMood.name)", for: .normal)
        addMoodButton?.backgroundColor = currentMood.color

        let selectionAnimator = UIViewPropertyAnimator(duration: ...