view_model.co

$J.ViewModel = $J.Emitter.extend do
  constructor: ->
    @initialize? ...
    @

  initialize: ->
    @views = {}
    @on '$J:sync:start', (view)~>
      @views[view.cid] = view
      if (_.keys @views)length is 1
        @connect!

    @on '$J:sync:end', (view)->
      delete @views[view.cid]
      if (_.keys @views)length is 0
        @disconnect!

  connect: (->)
  disconnect: (-> @stopListening!)

  sync: !->
    @trigger '$J:sync', ...@@