CATransition 动画主要在过渡时使用，比如两个页面层级改变的时候添加一个转场效果。CATransition 分为两类，一类是公开的动画效果，一类是非公开的动画效果。

1，公开动画效果：

• kCATransitionFade：翻页
• kCATransitionMoveIn：弹出
• kCATransitionPush：推出
• kCATransitionReveal：移除

2，非公开动画效果：

• "cube"：立方体
• "suckEffect"：吸收
• "oglFlip"：翻转
• "rippleEffect"：波纹
• "pageCurl"：卷页
• "cameraIrisHollowOpen"：镜头开
• "cameraIrisHollowClose"：镜头关

3，动画方向类型：

• kCATransitionFromRight：从右侧开始实现过渡动画
• kCATransitionFromLeft：从左侧开始实现过渡动画
• kCATransitionFromTop：从顶部开始实现过渡动画
• kCATransitionFromBottom：从底部开始实现过渡动画

import UIKit

class ViewController: UIViewController {
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        let redView:UIView = UIView(frame: CGRect(x:20, y:20, width:280, height:400))
        redView.backgroundColor = UIColor.red
        self.view.insertSubview(redView, at: 0)
        
        let blueView:UIView = UIView(frame: CGRect(x:20, y:20, width: 280, height:400))
        blueView.backgroundColor = UIColor.blue
        self.view.insertSubview(blueView, at: 1)
    }
    
    //点击切换两个红蓝视图
    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
        let transition = CATransition()
        transition.duration = 3.0
        transition.type = kCATransitionPush //推送类型
        transition.subtype = kCATransitionFromLeft //从左侧
        self.view.exchangeSubview(at: 1, withSubviewAt: 0)
        self.view.layer.add(transition, forKey: nil)
    }
    
    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
    }
}