View Resizer when Keyboard Appears

UIViewController.swift

// MARK: - View Resizer when Keyboard Appears

extension UIViewController {
    
    // This implementation was taken from: https://newfivefour.com/swift-ios-xcode-resizing-on-keyboard.html
    // to improve the user experience the view updates will happen with the same animation as the keyboard's
    
    func setupViewResizerOnKeyboardShown() {
        
        NotificationCenter.default.addObserver(self,
                                               selector: #selector(UIViewController.keyboardWillShowForResizing),
                                               name: Notification.Name.UIKeyboardWillShow,
                                               object: nil)
        
        NotificationCenter.default.addObserver(self,
                                               selector: #selector(UIViewController.keyboardWillHideForResizing),
                                               name: Notification.Name.UIKeyboardWillHide,
                                               object: nil)
    }
    
    @objc
    func keyboardWillHideForResizing(notification: Notification) {
        
        self.extractKeyboardUserInfo(notification.userInfo) { (keyboardSize) in
            
            let viewHeight = self.view.frame.height
            
            self.view.frame = CGRect(x: self.view.frame.origin.x,
                                     y: self.view.frame.origin.y,
                                     width: self.view.frame.width,
                                     height: viewHeight + keyboardSize.height)
        }
    }
    
    @objc
    func keyboardWillShowForResizing(notification: Notification) {
        
        // We're not just minusing the kb height from the view height because
        // the view could already have been resized for the keyboard before
        
        self.extractKeyboardUserInfo(notification.userInfo) { (keyboardSize) in
            
            guard let window = self.view.window?.frame else { return }
            
            self.view.frame = CGRect(x: self.view.frame.origin.x,
                                     y: self.view.frame.origin.y,
                                     width: self.view.frame.width,
                                     height: window.origin.y + window.height - keyboardSize.height)
        }
    }
    
    private func extractKeyboardUserInfo(_ userInfo: [AnyHashable: Any]?, andPerform animation: @escaping (CGRect) -> Void) {
        
        if let keyboardSize = (userInfo?[UIKeyboardFrameEndUserInfoKey] as? NSValue)?.cgRectValue {
            
            // extract animation duration and animation curve from the notification, so the UIView update occurs during the keyboard animation
            if let animationDuration = (userInfo?[UIKeyboardAnimationDurationUserInfoKey] as? NSNumber)?.doubleValue,
                let curveInteger = (userInfo?[UIKeyboardAnimationCurveUserInfoKey] as? NSNumber)?.uintValue {
                
                let animationCurve = UIViewAnimationOptions(rawValue: curveInteger)
                
                UIView.animate(withDuration: animationDuration, delay: 0.0, options: animationCurve, animations: {
                    
                    animation(keyboardSize)
                    
                }, completion: nil)
            }
            else {
                
                // for some weird reason we couldn't get the animation info, so just update the UIView with no animation
                animation(keyboardSize)
            }
        }
    }
}