From http://stackoverflow.com/questions/17510756/chaining-promises-in-coffeescript

example-coffee-promises.coffee

  $.getJSON('/api/post.json')
    .then (response) ->
      # do something
      response # if you would not return anything, promise would be fulfilled with undefined
    .then (response) ->
      # do something
      undefined # necessary to prevent non-empty function body
    .then null, (err) ->
      # handle error