UIViewController Extension to handle keyboard updates easily

UIViewController+Helpers.swift

import Foundation
import UIKit
import ReactiveSwift
import Result

extension UIViewController {

    typealias KeyboardStatusInfo = (height: CGFloat , duration: TimeInterval, animationOptions: UIViewAnimationOptions)

    var keyboardUpdatesSignal: Signal<KeyboardStatusInfo, NoError> {
        let center = NotificationCenter.default.reactive
        let willShowProducer = center.notifications(forName: .UIKeyboardWillShow).map {
            [weak self] (notification) -> KeyboardStatusInfo? in
            self?.parsekeyboardNotification(notification: notification)
        }.skipNil()

        let willHideProducer = center.notifications(forName: .UIKeyboardWillHide).map {
            [weak self] (notification) -> KeyboardStatusInfo? in
            self?.parsekeyboardNotification(notification: notification)
        }.skipNil()

        return Signal.merge([willShowProducer, willHideProducer])
    }

    func parsekeyboardNotification(notification: Notification) -> KeyboardStatusInfo? {
        guard UIApplication.shared.applicationState != .background else {
            return (0, 0, UIViewAnimationOptions.curveEaseInOut)
        }
        guard let info = notification.userInfo else {
            return nil
        }
        guard let frame = (info[UIKeyboardFrameEndUserInfoKey] as? NSValue)?.cgRectValue else {
            return nil
        }

        let height = UIScreen.main.bounds.height - frame.origin.y  // height above screen

        guard let duration = info[UIKeyboardAnimationDurationUserInfoKey] as? TimeInterval else {
            return nil
        }

        guard let curveRaw = info[UIKeyboardAnimationCurveUserInfoKey] as? Int else {
            return nil
        }

        let options = UIViewAnimationOptions(rawValue: UInt(curveRaw) << 16)

        return (height, duration, options)
    }

    var appDidEnterBGSignal: Signal<Notification, NoError> {
        return NotificationCenter.default.reactive.notifications(forName: .UIApplicationDidEnterBackground)
    }

    var appWillEnterFGSignal: Signal<Notification, NoError> {
        return NotificationCenter.default.reactive.notifications(forName: .UIApplicationWillEnterForeground)
    }
}