Gradually adding rectangle animation in iOS - ios

Question

I have a single view application in Xcode and doing the following in ViewController.swift. My objective is to have the screen filled up with a brown colored rectangle gradually over 5 seconds. Am I missing something or is the approach completely wrong?
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
let expandAnimation: CABasicAnimation = CABasicAnimation(keyPath: "path")
expandAnimation.fromValue = UIBezierPath(rect: CGRect(x: 0.0, y: 0.0, width: 0.0, height: 0.0))
expandAnimation.toValue = UIBezierPath(rect: CGRect(x: 0.0, y: 0.0, width: self.view.bounds.size.width, height: self.view.bounds.size.height))
expandAnimation.duration = 5.0
expandAnimation.fillMode = kCAFillModeForwards
expandAnimation.isRemovedOnCompletion = false
let rectLayer: CAShapeLayer = CAShapeLayer()
rectLayer.fillColor = UIColor.brown.cgColor
rectLayer.path = UIBezierPath(rect: CGRect(x: 0.0, y: 0.0, width: 0.0, height: 0.0)).cgPath
rectLayer.add(expandAnimation, forKey: nil)
self.view.layer.addSublayer(rectLayer)
}
I don't want the color to gradually appear. I want a glass filling kind of effect. Imagine this
except for the fancy wavy effects.

Answer 1

After understanding your question better, you want to simulate the filing of a water glass (without the animation of the wave), you can achieve that through:
let myLayer: CALayer = .init()
myLayer.backgroundColor = UIColor.red.cgColor
self.view.layer.addSublayer(myLayer)
func animateFilling(to view:UIView)
{
var mFrame = CGRect(x: 0, y: view.frame.size.height, width: view.frame.size.width, height: 0)
myLayer.frame = mFrame
let fillingAnim = CABasicAnimation(keyPath: "bounds")
fillingAnim.fillMode = kCAFillModeForwards
fillingAnim.fromValue = mFrame
fillingAnim.duration = 2
fillingAnim.isRemovedOnCompletion = false
mFrame.size.height = 1000
fillingAnim.toValue = mFrame
myLayer.add(fillingAnim, forKey: nil)
}

Answer 2

I think it's easy to do it like that if you don't want top wave
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
let vv = UIView(frame: CGRect(x: 0, y: self.view.bounds.size.height, width: self.view.bounds.size.width, height: 0))
vv.backgroundColor = UIColor.brown
self.view.addSubview(vv)
UIView.animate(withDuration: 5.0) {
vv.frame = CGRect(x: 0, y: self.view.bounds.size.height / 3.0, width: self.view.bounds.size.width, height: self.view.bounds.size.height * 2 / 3.0)
}
}