ActiveModel::Serializer Observations/edge-cases

README.md

Observation #1 (see included code):

App has 4 keys in a hash property called stats: '10s', '1min', '5min', 'day'. Each are arrays of Stat objects In order to create a stats attribute in AppSerializer, we have to create an intermediary Serializer with the attributes in order to re-use StatSerializer for each of those four Stat collections, and the syntax within that Serializer is pretty kludgy to make the association work.

Observation #2:

Using ActiveModel::Serializer outside of ActiveRecord requires an inclusion of ActiveModel::SerializerSupport, but the documentation does not state this, so there was some head-scratching as to why it wasn't magically working on our Mongoid models.

Observation #3 (see settings_serializer.rb):

I find instances where I have a hash attribute that I need to specify keys of the hash that I either need to write a filtered hash object or its own Serializer object. That may or may not be working-as-intended as this has some feeling of hash-driven mentality, but it surprised me.

Observation #4:

I cannot find a way to make the serializer data be the root of the JSON response, instead of being the data in a key. For example, if instead of wanting { 'app': { 'foo': 'bar' } } I want { 'foo': 'bar' }, there does not seem to be a way for that. I can change 'app' to 'foo' by passing the :root option, but I do not see a way to cause it to be the root of the JSON response itself.

app_serializer.rb

class AppSerializer < ActiveModel::Serializer
  attributes :id, :name

  has_one :stats, :serializer => AppStatsSerializer

  def stats
    app.stats
  end
end

app_stats_serializer.rb

class AppStatsSerializer < ActiveModel::Serializer
  has_many 'ten_stats', key: '10s', serializer: StatSerializer
  has_many 'one_stats', key: '1min', serializer: StatSerializer
  has_many 'five_stats', key: '5min', serializer: StatSerializer
  has_many 'day_stats', key: 'day', serializer: StatSerializer

  def ten_stats
    app_stats['10s']
  end

  def one_stats
    app_stats['1min']
  end

  def five_stats
    app_stats['5min']
  end

  def day_stats
    app_stats['day']
  end
end

settings_serializer.rb

class SettingsSerializer < ActiveModel::Serializer
  attributes :app_name

  has_one :pusher
  has_one :auth_info

  # pusher has app_id, key, and secret. we don't want secret passed.
  def pusher
    {
      app_id: settings.pusher.app_id,
      key: settings.pusher.key
    }
  end

  # auth_info has data from two properties in Settings we want in a
  # nested hash
  def auth_info
    {
       base_url: settings.auth_info.base_url,
       oauth: {
         client_id: settings.auth_info.oauth.client_id
       }
    }
  end
end

stat_serializer.rb

class StatSerializer < ActiveModel::Serializer
  attributes :stat, :values, :type, :ts, :date
end

I think one of my larger problems--once I realized that I had to include ActiveModel::SerializerSupport--is that I don't like having to overload the association-style methods this way, e.g. calling .has_one :pusher followed by def pusher; ... seems too obvious a kludge. But this is clearly the legacy of ActiveModel::Serializers being designed first and foremost to serialize normal-rails-style models.

So basically: I'm looking for a third sort of method beyond attributes and has_(one|many) that will allow me to specify additional output to be included in the serialization.

Por ejemplo, when I was rolling my own responders for scenarios like the first pair of examples here, I would have a method something like this:

def as_json(*)
   {
    "id" => @object.id,
    "name" => @object.name,
    "stats" => @object.stats.inject({}) do |accum, (k, data)|
      accum[k] = StatsPresenter.new(data); accum
    end
  }
end

Or failing that, the ability to use the same style of method definition on an attributes key as the has_(one|many) calls. My first instinct when I ran into this was attributes :pusher followed by def pusher ; ... ; end to modify the data getting passed as an attribute, only to see it doesn't work that way.