Info.md

I am trying to update a button's constraints when the keyboard is shown and hidden by adding/subtracting the keyboard's height from the constraint's constant.

I had this working previously, but after some re-factoring, it's stopped working. Previously, keyboardWillShow: and keyboardWillHide: were implemented exactly as shown below. I've since tried to use setNeedsUpdateConstraints and setNeedsLayout to try to force a refresh, to no avail.

When doing some simple print() debugging, buttonHorizontalConstraint.constant does get updated, but the changes just aren't reflected visually.

RegistrationNameView.swift

import UIKit

class RegistrationNameView: UIView {
    
    let questionLabel: UILabel = {
        let label = UILabel()
        
        label.font = UIFont.systemFontOfSize(21.0)
        label.text = "Hey, what's your name?"
        label.textAlignment = .Center
        label.textColor = UIColor.lightGrayColor()
        label.translatesAutoresizingMaskIntoConstraints = false
        
        return label
    }()
    let nameField: UITextField = {
        let field = UITextField()
        
        field.autocorrectionType = .No
        field.font = UIFont.boldSystemFontOfSize(28.0)
        field.placeholder = "Full name"
        field.returnKeyType = .Next
        field.textAlignment = .Center
        field.translatesAutoresizingMaskIntoConstraints = false
        
        return field
    }()
    let nextButton: UIButton = {
        let button = UIButton()
        
        button.setTitle("Continue", forState: .Normal)
        button.setTitleColor(UIColor.whiteColor(), forState: .Normal)
        button.titleLabel?.font = UIFont.boldSystemFontOfSize(17.0)
        button.backgroundColor = UIColor(red: 0.263, green: 0.910, blue: 0.847, alpha: 1)
        button.layer.cornerRadius = Global.UISizes.CornerRadius
        button.translatesAutoresizingMaskIntoConstraints = false
        button.contentEdgeInsets = UIEdgeInsetsMake(16.0, 0, 16.0, 0)
        
        return button
    }()
    
    var buttonHorizontalConstraint = NSLayoutConstraint()
    
    override init(frame: CGRect) {
        super.init(frame: frame)
        
        self.backgroundColor = UIColor.whiteColor()
        
        // Add subviews
        self.addSubview(questionLabel)
        self.addSubview(nameField)
        self.addSubview(nextButton)
        
        nameField.becomeFirstResponder()
        
        // Constraint helpers
        let spacer = Global.UISizes.SpacingUnit
        let margins = self.layoutMarginsGuide
        
        let layoutConstraints: [NSLayoutConstraint] = {
            var constraints = [NSLayoutConstraint]()
            
            // Title Label Constraints
            constraints.append(questionLabel.bottomAnchor.constraintEqualToAnchor(nameField.topAnchor, constant: -(spacer * 2)))
            constraints.append(questionLabel.leadingAnchor.constraintEqualToAnchor(margins.leadingAnchor))
            constraints.append(questionLabel.trailingAnchor.constraintEqualToAnchor(margins.trailingAnchor))
            
            // Description Label Constraints
            constraints.append(nameField.topAnchor.constraintEqualToAnchor(margins.centerYAnchor, constant: spacer * -12))
            constraints.append(nameField.leadingAnchor.constraintEqualToAnchor(margins.leadingAnchor))
            constraints.append(nameField.trailingAnchor.constraintEqualToAnchor(margins.trailingAnchor))
            
            // Sign Up Button Constraints
            self.buttonHorizontalConstraint = nextButton.bottomAnchor.constraintEqualToAnchor(margins.bottomAnchor, constant: -(spacer * 2))
            constraints.append(self.buttonHorizontalConstraint)
            constraints.append(nextButton.leadingAnchor.constraintEqualToAnchor(margins.leadingAnchor))
            constraints.append(nextButton.trailingAnchor.constraintEqualToAnchor(margins.trailingAnchor))
            
            return constraints
        }()
        NSLayoutConstraint.activateConstraints(layoutConstraints)
        
    }
    
    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    func keyboardWillShow(notification: NSNotification) {
        if let keyboardSize = (notification.userInfo! as NSDictionary).objectForKey(UIKeyboardFrameBeginUserInfoKey)?.CGRectValue.size {
            self.buttonHorizontalConstraint.constant -= keyboardSize.height
        }
    }
    
    func keyboardWillHide(notification: NSNotification) {
        if let keyboardSize = (notification.userInfo! as NSDictionary).objectForKey(UIKeyboardFrameBeginUserInfoKey)?.CGRectValue.size {
            self.buttonHorizontalConstraint.constant += keyboardSize.height
        }
    }

}

RegistrationNameViewController.swift

import Alamofire
import Locksmith
import UIKit

class RegistrationNameViewController: UIViewController {
    
    var nameView: RegistrationNameView! { return self.view as! RegistrationNameView }
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        let nameView = RegistrationNameView(frame: CGRectZero)
        nameView.nextButton.addTarget(self, action: "nextStep:", forControlEvents: .TouchUpInside)
        self.view = nameView
    }
    
    func nextStep(sender: AnyObject) {
        print("going to the next step \(sender)")
        
        let credentialsViewController = RegistrationCredentialsViewController()
        self.navigationController?.pushViewController(credentialsViewController, animated: true)
    }
    
}

RegistrationNavigationController.swift

import UIKit

class RegistrationNavigationController: UINavigationController, UINavigationControllerDelegate {
    
    var nameViewController: RegistrationNameViewController = RegistrationNameViewController()
    var credViewController: RegistrationCredentialsViewController = RegistrationCredentialsViewController()
    
    override init(rootViewController: UIViewController) {
        super.init(rootViewController: rootViewController)
        
        self.delegate = self
    }
    
    override init(nibName nibNameOrNil: String?, bundle nibBundleOrNil: NSBundle?) {
        super.init(nibName: nibNameOrNil, bundle: nibBundleOrNil)
    }
    
    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
    }
    
    func navigationController(navigationController: UINavigationController, willShowViewController viewController: UIViewController, animated: Bool) {
        
        let type = String(viewController.dynamicType)
        
        switch type {
        case "RegistrationNameViewController":
            // Add keyboard notifications to RegistrationNameViewController
            NSNotificationCenter.defaultCenter().addObserver(nameViewController.view,
                selector: "keyboardWillShow:", name: UIKeyboardWillShowNotification, object: nil)
            NSNotificationCenter.defaultCenter().addObserver(nameViewController.view,
                selector: "keyboardWillHide:", name: UIKeyboardWillHideNotification, object: nil)
            
        case "RegistrationCredentialsViewController":
            // Remove keyboard notifications to RegistrationNameViewController before
            // registering for new notifications
            NSNotificationCenter.defaultCenter().removeObserver(nameViewController.view)
            
            // Add keyboard notifications to RegistrationCredentialsViewController
            NSNotificationCenter.defaultCenter().addObserver(credViewController.view,
                selector: "keyboardWillShow:", name: UIKeyboardWillShowNotification, object: nil)
            NSNotificationCenter.defaultCenter().addObserver(credViewController.view,
                selector: "keyboardWillHide:", name: UIKeyboardWillHideNotification, object: nil)
            
        default:
            print("Default")
        }
        
    }
    
}