iOS 文字 逐字显示

class ViewController1: BaseViewController {
var textView = UITextView.init()
var poem = [("Test ", 0.2), ("my ", 0.2), ("core ", 0.2), ("just ", 0.2), ("like ", 0.2), ("before", 0.2)]

func display(poem: [(word: String, delay: TimeInterval)]) {
    guard let first = poem.first else { return }

    UIView.transition(with: textView,
                      duration: first.delay,
                      options: .transitionCrossDissolve,
                      animations: { self.textView.text.append(first.word) },
                      completion: nil)

    DispatchQueue.main.asyncAfter(deadline: .now() + first.delay) {
        self.display(poem: Array(poem.dropFirst()))
    }
}

}