オブザーバモードとパブリッシュ/サブスクリプションモード

オブザーバモード

コンセプト

インプリメンテーション

function ObserverList() {
  this.observerList = []
}

ObserverList.prototype.add = function(obj) {
  return this.observerList.push(obj)
}

ObserverList.prototype.Empty = function() {
  this.observerList = []
}

ObserverList.prototype.removeAt = function(index) {
  this.observerList.splice(index, 1)
}

ObserverList.prototype.count = function() {
  return this.observerList.length
}

ObserverList.prototype.get = function(index) {
  if (index > -1 && index < this.observerList.length) {
    return this.observerList[index]
  }
}

// Extend an object with an extension
function extend(extension, obj) {
  for (var key in extension) {
    obj[key] = extension[key]
  }
}

function Subject() {
  this.observers = new ObserverList()
}

Subject.prototype.addObserver = function(observer) {
  this.observers.add(observer)
}

Subject.prototype.removeObserver = function(observer) {
  this.observers.removeAt(this.observers.IndexOf(observer, 0))
}

Subject.prototype.notify = function(context) {
  var observerCount = this.observers.count()

  for (var i = 0; i < observerCount; i++) {
    this.observers.get(i).update(context)
  }
}

function Observer() {
  this.update = function() {
    // ...
  }
}

サンプル適用

Add New Observer checkbox

// DOM      
var controlCheckbox = document.getElementById('mainCheckbox'),
  addBtn = document.getElementById('addNewObserver'),
  container = document.getElementById('observersContainer')

//        

// Subject     controlCheckbox
extend(new Subject(), controlCheckbox)

//   checkbox            
controlCheckbox['onclick'] = new Function(
  'controlCheckbox.notify(controlCheckbox.checked)'
)

addBtn['onclick'] = AddNewObserver

//       

function AddNewObserver() {
  //             checkbox
  var check = document.createElement('input')
  check.type = 'checkbox'

  //    Observer     checkbox
  extend(new Observer(), check)

  //       update     
  check.update = function(value) {
    this.checked = value
  }

  //                         
  controlCheckbox.AddObserver(check)

  //            
  container.appendChild(check)
}

パブリッシュ/サブスクリプションモード

インプリメンテーション

var pubsub = {}

;(function(q) {
  var topics = {},
    subUid = -1

  // Publish or broadcast events of interest
  // with a specific topic name and arguments
  // such as the data to pass along
  q.publish = function(topic, args) {
    if (!topics[topic]) {
      return false
    }

    var subscribers = topics[topic],
      len = subscribers ? subscribers.length : 0

    while (len--) {
      subscribers[len].func(topic, args)
    }

    return this
  }

  // Subscribe to events of interest
  // with a specific topic name and a
  // callback function, to be executed
  // when the topic/event is observed
  q.subscribe = function(topic, func) {
    if (!topics[topic]) {
      topics[topic] = []
    }

    var token = (++subUid).toString()
    topics[topic].push({
      token: token,
      func: func
    })
    return token
  }

  // Unsubscribe from a specific
  // topic, based on a tokenized reference
  // to the subscription
  q.unsubscribe = function(token) {
    for (var m in topics) {
      if (topics[m]) {
        for (var i = 0, j = topics[m].length; i < j; i++) {
          if (topics[m][i].token === token) {
            topics[m].splice(i, 1)
            return token
          }
        }
      }
    }
    return this
  }
})(pubsub)

サンプル適用1

// Another simple message handler

// A simple message logger that logs any topics and data received through our
// subscriber
var messageLogger = function(topics, data) {
  console.log('Logging: ' + topics + ': ' + data)
}

// Subscribers listen for topics they have subscribed to and
// invoke a callback function (e.g messageLogger) once a new
// notification is broadcast on that topic
var subscription = pubsub.subscribe('inbox/newMessage', messageLogger)

// Publishers are in charge of publishing topics or notifications of
// interest to the application. e.g:

pubsub.publish('inbox/newMessage', 'hello world!')

// or
pubsub.publish('inbox/newMessage', ['test', 'a', 'b', 'c'])

// or
pubsub.publish('inbox/newMessage', {
  sender: '[email protected]',
  body: 'Hey again!'
})

// We cab also unsubscribe if we no longer wish for our subscribers
// to be notified
// pubsub.unsubscribe( subscription );

// Once unsubscribed, this for example won't result in our
// messageLogger being executed as the subscriber is
// no longer listening
pubsub.publish('inbox/newMessage', 'Hello! are you still there?')

サンプル適用2

$.ajax('http:// xxx.com?login', function(data) {
  header.setAvatar(data.avatar) //    header      
  nav.setAvatar(data.avatar) //          
})

$.ajax('http:// xxx.com?login', function(data) {
  pubsub.publish('loginSucc', data) //          
})

// header   
var header = (function() {
  pubsub.subscribe('loginSucc', function(data) {
    header.setAvatar(data.avatar)
  })

  return {
    setAvatar: function(data) {
      console.log('   header      ')
    }
  }
})()

// nav   
var nav = (function() {
  pubsub.subscribe('loginSucc', function(data) {
    nav.setAvatar(data.avatar)
  })

  return {
    setAvatar: function(avatar) {
      console.log('   nav      ')
    }
  }
})()

メリット

欠点

両者の相違

controlCheckbox.AddObserver(check)