gistfile1.coffee

App.ServerValidatedTextField = Ember.View.extend
  tagName: 'input'
  type: 'text'
  
  ###
    This is handy if you want your server to validate an input field.
    Your server is expected to return a boolean value
    When that `validInput` attribute changes, we'll replace the layoutTemplate
      with something that indicates valid or invalid.
    You'll need three templates: `_loadingTemplate`, `_validTemplate`, `_invalidTemplate`
  ###

  # specify a url and we'll make a GET request that expects a bool response
  # alternatively, you can overwrite the `validateInputValue` function
  # and instantiate this view with it
  url: null
  
  # the textfield is not validate to begin with
  validInput: false

  focusOut: -> @validateInputValue()

  validateInputValue: ->
    # if no url is defined, we won't do anything
    return if !@get('url')?
    # interim layout
    @set('layoutName', '_loadingTemplate')

    $.get url, (bool) =>
      if typeof bool is "boolean"
        @set('validInput', bool)
      else
        Ember.assert('The server did not return a boolean value')

  changeLayout: (->
    templateName = if @get('validInput') == true then '_validTemplate' else '_invalidTemplate'
    @set('layoutName', templateName)
  ).observes('validInput')