Error with UITextField moving - ios

Question

I'm trying to design a view within my app that displays an error UILabel when the text inside of a UITextField does not match a certain regex. Everything works fine except for when my UITextField contains an invalid entry and then I tap the screen to dismiss the keyboard. After the keyboard dismisses, the UITextField moves on top of my UITextView (the red text) and I cannot find out why. I have set breakpoints in my code, but it seems that none of my code is executed after the keyboard dismisses. Any help is appreciated.
//
// ViewController.swift
// KeyboardLabel
//
import UIKit
class ViewController: UIViewController {
#IBOutlet var titleLabel:UILabel!
#IBOutlet var errorLabel:UITextView!
#IBOutlet var textBox:UITextField!
#IBOutlet var createButton:UIButton!
var deltaHeight:CGFloat!
var beenMoved = true
override func viewDidLoad() {
super.viewDidLoad()
// Register for notifications when the text in the text field is changed
NSNotificationCenter.defaultCenter().addObserver(self, selector: "validateText", name: UITextFieldTextDidChangeNotification, object: textBox)
// Add a gesture recognizer to dismiss the keyboard
view.addGestureRecognizer(UITapGestureRecognizer(target: self, action: "dismissKeyboard"))
// Set the text of the labels
titleLabel.text = "Container Number:"
errorLabel.text = "Error, Invalid container number.\nRe-enter number."
// Calculate the height to move the text field and button
deltaHeight = errorLabel.frame.size.height + 8.0
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
func dismissKeyboard() {
textBox.resignFirstResponder()
}
func validateText() {
dispatch_async(dispatch_get_main_queue(), {
// Regular expression for determining whether the text is valid
let predicate = NSPredicate(format: "SELF MATCHES %#", "[a-zA-Z0-9#]+")
let empty = self.textBox.text!.isEmpty
let valid = predicate.evaluateWithObject(self.textBox.text)
// If the string is valid
if valid || empty {
// If the view has been moved down
if(!self.beenMoved) {
// Hide the error label then move the text field and create button up
self.errorLabel.hidden = true
UIView.animateWithDuration(0.4, animations: {
self.textBox.frame.origin.y -= self.deltaHeight
self.createButton.frame.origin.y -= self.deltaHeight
})
// Flip the flag
self.beenMoved = true
}
}
// If the string is invalid
else {
// If the view has been moved up
if(self.beenMoved) {
// Show the error label then move the text field and create button down
UIView.animateWithDuration(0.4, animations: {
self.textBox.frame.origin.y += self.deltaHeight
self.createButton.frame.origin.y += self.deltaHeight
}, completion: {
(flag:Bool) in
self.errorLabel.hidden = false
})
// Flip the flag
self.beenMoved = false
}
}
// If the text field is empty
if empty {
// Disable the create button
self.createButton.enabled = false
}
else {
// Enable the create button
self.createButton.enabled = true
}
})
}
}

Answer 1

The behavior is actually such that initially, the UITextField moves on top of the UITextView if you enter something that does not match the regex. This is because you are moving the UITextField and button with the following lines of code:
self.textBox.frame.origin.y += self.deltaHeight
self.createButton.frame.origin.y += self.deltaHeight
When the keyboard dismisses, the UITextField and UIButton return to their original locations. I am assuming you have no constraints on the UI elements.