Technique for ensuring you have the info you need, and it's up to date

act.coffee

act: (context, f, keyPaths...) ->
  ok = true
  for k in keyPaths
    if !context.get(k)?
      ok = false
      context.observe k, (newValue, oldValue, keyPath) =>
        ok = true
        for k in keyPaths
          ok = context.get(k)?
          return unless ok
        f.apply(context) if ok
  f.apply(context) if ok

setupCalendar: ->
  @set '$', App.stateManager
  @act @, @getCalendar, '$.user.grade', '$.user.program'

getCalendar: ->
  _grade = App.stateManager.get('user.grade')
  _program = App.stateManager.get('user.program')
  console.log 'getCalendar', _grade, _program
  App.CouchStorage.view 'calendar', {key: ["#{_grade}", "#{_program}", App.Calendar.unit(_program)]}, (err, results) ->
    if err?
      throw err
    if !results?.length
      alert 'Creating new calendar document'
      App.calendar = new App.Calendar
      setTimeout (=> App.calendar.save()), 1000
      App.fire 'calendar_ready'
    else
      App.calendar = results.toArray()[0]
      console.log 'Calendar pre-existed', App.calendar.get('id')
      App.fire 'calendar_ready'

dude.coffee

class Dude extends Batman.Object

  act: (context, f, keyPaths...) ->
    ok = true
    for k in keyPaths
      if !context.get(k)?
        ok = false
        context.observe k, (newValue, oldValue, keyPath) =>
          ok = true
          for k in keyPaths
            ok = context.get(k)?
            return unless ok
          f.apply(context) if ok
    f.apply(context) if ok
  
  
  test: ->
    @act @, @ready, 'crack', 'head'
    setTimeout((=> @set('crack','$')), 500)
    setTimeout((=> @set('head','$')), 1000)
    setTimeout((=> @unset('crack')), 2000)
    setTimeout((=> @set('head','¢')), 2500)
    setTimeout((=> @set('crack','€')), 3250)
    'testing...'
  
  ready: ->
    console.log @get('crack'), @get('head')

dude = new Dude()

dude.test() 

### RESULTS:
testing... (0 sec)
$ $ (1 sec)
€ ¢ (3.25 sec)
###