gistfile1.coffee

# Multiple models/collections event tracking
# ==========================================
#
# This is handy, for instance, when something needs to happen once a set
# of collections fire `sync`. For example:
#
#   Backbone.Events.when [User, Projects], 'sync', ->
#     alert 'carry on with all the data ready'

Backbone.Events.when = (models, track, callback) ->
  done = []
  _.each models, (model) ->
    model.once track, ->
      done = _.union done, [model]
      callback() if _.isEmpty _.difference(models, done)