textField SlideAnimation when starting initial view controller - ios

Question

I need to create a right slide animation for TextField 1 and left slide animation for TextField2 . I tried to accomplish first right slide animation, but there is a problem. I have an slide animation, but there is another textfield under my animation textfield which doesn't move from it's constraints. I do not really understand why.
here is the code:
class ViewController: UIViewController {
#IBOutlet weak var emailField: UITextField!
#IBOutlet weak var PasswordField: UITextField!
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
}
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
emailField.center.x = self.view.frame.width + 50
UIView.animate(withDuration: 1.0, delay: 0.0, usingSpringWithDamping: 1.0, initialSpringVelocity: 1.0, options: .allowAnimatedContent, animations: {
self.emailField.center.x = self.view.frame.width/2
self.view.layoutIfNeeded()
}, completion: nil)
}
}

Answer 1

Assuming your Storyboard looks similar to this:
Two text fields, with Top constraints, Width constraints equal to 80% of the view width, and CenterX constraints to the view's CenterX
Ctrl-Drag from each .centerX constraint to your view controller code to create #IBOutlet connections to the constraints:
#IBOutlet var emailCenterX: NSLayoutConstraint!
#IBOutlet var passwordCenterX: NSLayoutConstraint!
Your Storyboard will now look like this:
And you can move / animate the views by setting their .constant values at run-time:
class AViewController: UIViewController {
#IBOutlet var emailField: UITextField!
#IBOutlet var PasswordField: UITextField!
#IBOutlet var emailCenterX: NSLayoutConstraint!
#IBOutlet var passwordCenterX: NSLayoutConstraint!
var viewWidth: CGFloat = 0
override func viewDidLoad() {
super.viewDidLoad()
// move the textFields "off-screen"
emailCenterX.constant = UIScreen.main.bounds.width
passwordCenterX.constant = -UIScreen.main.bounds.width
}
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
// reset the centerX constraints to the center of the view
emailCenterX.constant = 0
passwordCenterX.constant = 0
UIView.animate(withDuration: 1.0, delay: 0.0, usingSpringWithDamping: 1.0, initialSpringVelocity: 1.0, options: .allowAnimatedContent, animations: {
self.view.layoutIfNeeded()
}, completion: nil)
}
}