Simple pubsub implementation in Swift

pubsub.swift

// =====================================================

enum LogLevel: Int {
    case Debug = 1, Info, Error
}

let log_level = LogLevel.Debug

protocol Loggable {
    func log()
    func log_error()
    func log_debug()
}

extension String: Loggable {
    func log() {
        if log_level.toRaw() <= LogLevel.Info.toRaw() {
            println("[info]\t\(self)")
        }
    }
    
    func log_error() {
        if log_level.toRaw() <= LogLevel.Error.toRaw() {
            println("[error]\t\(self)")
        }
    }
    
    func log_debug() {
        if log_level.toRaw() <= LogLevel.Debug.toRaw() {
            println("[debug]\t\(self)")
        }
    }
}

// =====================================================

typealias Callback = () -> ()

struct Event {
    static var events = Dictionary<String, Array<Callback>>()
    
    static func register(event: String, callback: Callback) {
        if !self.events[event] {
            "Initializing list for event '\(event)'".log_debug()
            self.events[event] = Array<Callback>()
        }
        
        if var callbacks = self.events[event] {
            callbacks.append(callback)
            self.events[event] = callbacks
            "Registered callback for event '\(event)'".log_debug()
        } else {
            "Failed to register callback for event \(event)".log_error()
        }
    }
    
    static func emit(event: String) {
        "Emitting event '\(event)'".log_debug()
        if let events = self.events[event] {
            "Found list for event '\(event)', of length \(events.count)".log_debug()
            for callback in events {
                callback()
            }
        } else {
            "Could not find callbacks for event '\(event)'".log_error()
        }
    }
}

// =====================================================

protocol Evented {
    func emit(message: String) -> Bool
}

class Foo: Evented {
    var name: String {
    willSet(newName) {
        self.emit("Name changed to \(newName)")
    }
    }
    
    init(name: String) {
        self.name = name
        let evtName = "start"
        Event.register(evtName) {
            "The show is starting!".log()
        }
    }
    
    func emit(message: String) -> Bool {
        message.log_debug()
        return true
    }
}

// =====================================================

let myFoo = Foo(name: "Jahfer")
Event.emit("start")

myFoo.name = "Jeff"
myFoo.name = "Mary"


// Outputs:
// -----------------------------------------------------
// [debug]	Initializing list for event 'start'
// [debug]	Registered callback for event 'start'
// [debug]	Emitting event 'start'
// [debug]	Found list for event 'start', of length 1
// [info]	The show is starting!
// [debug]	Name changed to Jeff
// [debug]	Name changed to Mary