Looping with animations - swift

Question

I have this code
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
//'img' is a picture imported in your project
self.mrock.image = UIImage(named: "bird")
self.rrock.image = UIImage(named: "rock2")
self.lrock.image = UIImage(named: "rock3")
}
override func viewDidAppear(animated: Bool) {
super.viewDidAppear(animated)
if rockNamesArray[1] == "rock2" {
let firstPos: CGFloat = 300.0
UIView.animateWithDuration(3.0, animations: { () -> Void in
self.mrock.frame = CGRectMake(167, 600, CGFloat(self.mrock.bounds.size.width), CGFloat(self.mrock.bounds.size.height))
})}
if rockNamesArray[2] == "rock3" {
let secondPos: CGFloat = 300.0
UIView.animateWithDuration(3.0, animations: { () -> Void in
self.rrock.frame = CGRectMake(220, 600, CGFloat(self.rrock.bounds.size.width), CGFloat(self.rrock.bounds.size.height))
})}
if rockNamesArray[0] == "bird" {
let thirdPos: CGFloat = 300.0
UIView.animateWithDuration(3.0, animations: { () -> Void in
self.lrock.frame = CGRectMake(115, 600, CGFloat(self.lrock.bounds.size.width), CGFloat(self.lrock.bounds.size.height))
})}
And I would like to know how to make it so that when the png reaches the end of the screen, that it goes back to its original position, how would I do this?

Answer 1

If I understand your question correctly, you can pass a completion closure to UIView.animateWithDuration that will be executed once your animation is complete. In the closure you can make the view return to its original position, for example:
override func viewDidAppear(animated: Bool) {
super.viewDidAppear(animated)
let originalFrame = lrock.frame
UIView.animateWithDuration(3.0, animations: {
lrock.frame = CGRect(origin: CGPoint(x: 115, y: 600), size: lrock.frame.size)
},
completion: { _ in
lrock.frame = originalFrame
})
}