为文本视图中的文本制作动画(swift3)

import UIKit

class ViewController: UIViewController {
    @IBOutlet weak var textView: UITextView!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        // 初始时将文本视图的透明度设置为0
        textView.alpha = 0
    }
    
    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        
        // 使用UIView的动画功能为文本视图添加淡入淡出的效果
        UIView.animate(withDuration: 1.0, delay: 0.0, options: [.autoreverse, .repeat], animations: {
            self.textView.alpha = 1.0
        }, completion: nil)
    }
}