Notification with enum.

NSNotificationObservable.swift

import Foundation
import UIKit

enum NotificationKey: String {
    case Hoge
}

//--------------- pattern1: use protocol-extension
protocol NSNotificationObservable: RawRepresentable {
    var rawValue: String { get }
}

extension NSNotificationObservable {
    func addObserver(observer: AnyObject, selector: Selector, object: AnyObject? = nil) {
        NSNotificationCenter.defaultCenter().addObserver(observer, selector: selector, name: self.rawValue, object: object)
    }
    
    func addObserver(object: AnyObject? = nil, queue: NSOperationQueue? = nil, usingBlock block: NSNotification -> Void) -> NSObjectProtocol {
        return NSNotificationCenter.defaultCenter().addObserverForName(self.rawValue, object: object, queue: queue, usingBlock: block)
    }

    
    func post(object: AnyObject? = nil, userInfo: [NSObject: AnyObject]? = nil) {
        NSNotificationCenter.defaultCenter().postNotificationName(self.rawValue, object: object, userInfo: userInfo)
    }
    
    func removeObserver(observer: AnyObject, object: AnyObject? = nil) {
        NSNotificationCenter.defaultCenter().removeObserver(observer, name: self.rawValue, object: object)
    }
}

// adapt NotificationObservable to NotificationKey enum
extension NotificationKey: NSNotificationObservable {}


//-------------- pattern2 : extend NSNotificationCenter for enum key
public extension NSNotificationCenter {
    func addObserver<Key: RawRepresentable where Key.RawValue == String>(observer: AnyObject, selector aSelector: Selector, key: Key?, object anObject: AnyObject?) {
        self.addObserver(observer, selector: aSelector, name: key?.rawValue, object: anObject)
    }
    func postNotificationKey<Key: RawRepresentable where Key.RawValue == String>(key: Key, object anObject: AnyObject?) {
        self.postNotificationName(key.rawValue, object: anObject)
    }
    func postNotificationKey<Key: RawRepresentable where Key.RawValue == String>(key: Key, object anObject: AnyObject?, userInfo aUserInfo: [NSObject : AnyObject]?) {
        self.postNotificationName(key.rawValue, object: anObject, userInfo: aUserInfo)
    }
    
    func removeObserver<Key: RawRepresentable where Key.RawValue == String>(observer: AnyObject, key: Key?, object anObject: AnyObject?) {
        self.removeObserver(observer, name: key?.rawValue, object: anObject)
    }
    
    
    func addObserverForKey<Key: RawRepresentable where Key.RawValue == String>(key: Key?, object obj: AnyObject?, queue: NSOperationQueue?, usingBlock block: (NSNotification) -> Void) -> NSObjectProtocol {
        return self.addObserverForName(key?.rawValue, object: obj, queue: queue, usingBlock: block)
    }
}


class AAA {
    @objc func hoge() {
        print("!!!!!")
    }
}

let anObject = AAA()

// example: pattern1
NotificationKey.Hoge.addObserver(anObject, selector: #selector(anObject.hoge))
NotificationKey.Hoge.post()
NotificationKey.Hoge.removeObserver(anObject)

// example: pattern2
NSNotificationCenter.defaultCenter().addObserver(anObject, selector: #selector(anObject.hoge), key: NotificationKey.Hoge, object: nil)
NSNotificationCenter.defaultCenter().postNotificationKey(NotificationKey.Hoge, object: nil)
NSNotificationCenter.defaultCenter().removeObserver(anObject, key: NotificationKey.Hoge, object: nil)

// ---- normal usage
NSNotificationCenter.defaultCenter().addObserver(anObject, selector: #selector(anObject.hoge), name: NotificationKey.Hoge.rawValue, object: nil)
NSNotificationCenter.defaultCenter().postNotificationName(NotificationKey.rawValue, object: nil)
NSNotificationCenter.defaultCenter().removeObserver(anObject, name: NotificationKey.Hoge.rawValue, object: nil)