Polymorphic relatedModel for backbone-associations

models.coffee

{polymorphic} = require 'polymorphic'

class OtherModel extends Backbone.Model

class YetAnotherOtherModel extends Backbone.Model

class MyModel extends Backbone.Model
  relations: [
    type: Backbone.One
    key: 'otherUri'
    relatedModel: polymorphic 'otherUri', OtherModel, YetAnotherOtherModel
  ]

polymorphic.coffee

# Provides polymorphic relations
polymorphic = (key) ->

  # Allow a list of models or multiple arguments
  if _.isArray arguments[1]
    models = arguments[1]
  else
    models = []

    # Arguments isn't an array / doesn't have slice, so
    # we'll have to do this the old fashion way.
    i = 1

    while i < arguments.length
      models.push arguments[i]
      ++i

  # Maps a specific model instance to it's related model type
  mapper = (attributes) ->
    for relation in @relations
      if relation.key == key
        break

    identifier = attributes[relation.key] or @get relation.key

    for model in models
      if identifier?
        searchIndex = identifier.indexOf model.prototype.urlRoot

        if searchIndex == 0
          console.dir attributes
          console.dir @
          return model

  return mapper 


module.exports = {polymorphic}

Note that "key" would not be necessary in the polymorphic function if this were available:

dhruvaray/backbone-associations#50