For control flow, we have to absolutely know that a promise is resolved. This is a small pattern I've used in isolation that I would like nitpicked.

promise_accessors_with_blocking.coffee

class BananaStand extends Batman.Object
  @accessor 'hasMoney', promise: (deliver) ->
    new Batman.Request
      url: "/banana_stand/has_money.json" # true, false
      success: (json) ->
        deliver(null, json)
    return undefined
    
  onResolved: (path, callback) ->
    if @get(path) == undefined
      @observeOnce path, callback
    else
      callback()
      
stand = new BananaStand()

stand.onResolved 'hasMoney', =>
  if stand.get('hasMoney')
    # do stuff