KeyboardSizeManager - Swift class to help adjust UI when the keyboard appears and disappears

KeyboardSizeManager.swift

import Foundation
import UIKit

final class KeyboardSizeManager {

    private weak var bottomConstraint: NSLayoutConstraint?

    private var oldValue: CGFloat

    // MARK: - Init

    public init(bottomConstraint: NSLayoutConstraint) {
        self.bottomConstraint = bottomConstraint
        oldValue = bottomConstraint.constant
        addObservers()
    }

    deinit {
        removeObservers()
    }

    private func addObservers() {
        NotificationCenter.default.addObserver(
            self,
            selector: #selector(handleKeyboardChangeNotification(_:)),
            name: UIResponder.keyboardWillChangeFrameNotification,
            object: nil
        )
        NotificationCenter.default.addObserver(
            self,
            selector: #selector(handleKeyboardWillHideNotification(_:)),
            name: UIResponder.keyboardWillHideNotification,
            object: nil
        )
    }

    private func removeObservers() {
        NotificationCenter.default.removeObserver(self, name: UIResponder.keyboardWillChangeFrameNotification, object: nil)
        NotificationCenter.default.removeObserver(self, name: UIResponder.keyboardWillHideNotification, object: nil)
    }

    // MARK: - Keyboard

    @objc private func handleKeyboardChangeNotification(_ notification: Notification) {
        let keyboardFrame = (notification.userInfo?[UIResponder.keyboardFrameEndUserInfoKey] as? NSValue)?.cgRectValue
        configureKeyboard(frame: keyboardFrame, notification: notification)
    }

    @objc private func handleKeyboardWillHideNotification(_ notification: Notification) {
        configureKeyboard(frame: nil, notification: notification)
    }

    private func configureKeyboard(frame: CGRect?, notification: Notification) {
        let curve = (notification.userInfo?[UIResponder.keyboardAnimationCurveUserInfoKey] as? NSNumber)?.uintValue
        let duration = (notification.userInfo?[UIResponder.keyboardAnimationDurationUserInfoKey] as? NSNumber)?.doubleValue
        let options = UIView.AnimationOptions(rawValue: (curve ?? 0) << 16)
        let keyboardFrame = frame ?? .zero

        UIView.animate(
            withDuration: duration ?? 0,
            delay: 0,
            options: options,
            animations: {
                guard let constraint = self.bottomConstraint else { return }

                let isHiding = frame == nil
                if isHiding {
                    constraint.constant = self.oldValue
                } else {
                    constraint.constant = -keyboardFrame.height
                }
            },
            completion: nil
        )
    }
}