// .keyboardWillShow is a static property.
Notice.Center.default.observe(name: .keyboardWillShow) { keyboardInfo in
    // In this case, keyboardInfo is UIKeyboardInfo type.
    // It is inferred from a generic parameter of Notice.Name<Value>.
    print(keyboardInfo)
}
// pool is Notice.ObserverPool.
// If pool is released, Notice.Observes are automatically removed.
.invalidated(by: pool)

extension Notice.Names {
    static let keyboardWillShow = Notice.Name<UIKeyboardInfo>(UIResponder.keyboardWillShowNotification)
}

struct UIKeyboardInfo: NoticeUserInfoDecodable {
    let frame: CGRect
    let animationDuration: TimeInterval
    let animationCurve: UIViewAnimationOptions

    init?(info: [AnyHashable : Any]) {
        guard
            let frame = (info[UIKeyboardFrameEndUserInfoKey] as? NSValue)?.cgRectValue,
            let duration = info[UIKeyboardAnimationDurationUserInfoKey] as? TimeInterval,
            let curve = info[UIKeyboardAnimationCurveUserInfoKey] as? UInt
        else {
            return nil
        }
        self.frame = frame
        self.animationDuration = duration
        self.animationCurve = UIViewAnimationOptions(rawValue: curve)
    }
}

extension Notice.Names {
    static let navigationControllerDidShow = Notice.Name<NavigationControllerContent>(name: "navigationControllerDidShow")
}

let content = NavigationControllerContent(viewController: viewController, animated: animated)
Notice.Center.default.post(name: .navigationControllerDidShow, value: content)

let observer = Notice.Center.default.observe(name: .keyboardWillShow) { keyboardInfo in
    print(keyboardInfo)
}
observer.invalidate()

NotificationCenter.default.nok.observe(name: .keyboardWillShow) { keyboardInfo in
    print(keyboardInfo)
}
.invalidated(by: pool)

import UIKit
import NoticeObserveKit

class ViewController: UIViewController {
    private let searchBar = UISearchBar(frame: .zero)
    private var pool = Notice.ObserverPool()

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        navigationItem.titleView = searchBar

        configureObservers()
    }

    private func configureObservers() {
        Notice.Center.default.observe(name: .keyboardWillShow) {
            print("UIKeyboard will show = \($0)")
        }.invalidated(by: pool)

        Notice.Center.default.observe(name: .keyboardWillHide) {
            print("UIKeyboard will hide = \($0)")
        }.invalidated(by: pool)
    }
}