Question

I use Rails 3.0.6 with mongoID 2.0.2. Recently I encountered an issue with save! method when overriding setter (I am trying to create my own nested attributes).

So here is the model:

class FeedItem
  include Mongoid::Document
  has_many :audio_refs

  def audio_refs=(attributes_array, binding)

    attributes_array.each do |attributes|
      if attributes[:audio_track][:id]
        self.audio_refs.build(:audio_track => AudioTrack.find(attributes[:audio_track][:id]))
      elsif attributes[:audio_track][:file]
        self.audio_refs.build(:audio_track => AudioTrack.new(:user_id => attributes[:audio_track][:user_id], :file => attributes[:audio_track][:file]))
      end
    end

    if !binding
      self.save!
    end
  end

AudioRef model (which is just buffer between audio_tracks and feed_items) is:

class AudioRef
  include Mongoid::Document

  belongs_to :feed_item
  belongs_to :audio_track

end

And AudioTrack:

class AudioTrack
  include Mongoid::Document
  has_many :audio_refs
  mount_uploader :file, AudioUploader
end

So here is the spec for the FeedItem model which doesn`t work:

  it "Should create audio_track and add audio_ref" do
      @audio_track = Fabricate(:audio_track, :user_id => @author.id, :file => File.open("#{Rails.root}/spec/stuff/test.mp3"))
      @feed_item= FeedItem.new(
        :user => @author,
        :message => {:body => Faker::Lorem.sentence(4)},
        :audio_refs => [
            {:audio_track => {:id => @audio_track.id}},
            {:audio_track => {:user_id => @author.id, :file => File.open("#{Rails.root}/spec/stuff/test.mp3")}}
        ]
      )
      @feed_item.save!          
      @feed_item.reload
      @feed_item.audio_refs.length.should be(2)
  end

As you can see, the reason I am overriding audio_refs= method is that FeedItem can be created from existing AudioTracks (when there is params[:audio_track][:id]) or from uploaded file (params[:audio_track][:file]).

The problem is that @feed_item.audio_refs.length == 0 when I run this spec, i.e. audio_refs are not saved. Could you please help me with that?

Some investigation:

1) binding param is “true” by default (this means we are in building mode)

Answer 1

I found a solution to my problem but I didnt understand why save method doesnt work and didn`t make my code work. So first of all let me describe my investigations about the problem. After audio_refs= is called an array of audio_refs is created BUT in any audio_ref is no feed_item_id. Probably it is because the feed_item is not saved by the moment.

So the solution is quite simple – Virtual Attributes. To understand them watch corresponding railscasts

So my solution is to create audio_refs by means of callback “after_save”

I slightly changed my models:

In FeedItem.rb I added

attr_writer :audio_tracks #feed_item operates with audio_tracks array
after_save :assign_audio #method to be called on callback

def assign_audio
    if @audio_tracks
      @audio_tracks.each do |attributes|
        if attributes[:id]
          self.audio_refs << AudioRef.new(:audio_track => AudioTrack.find(attributes[:id]))
        elsif attributes[:file]
          self.audio_refs << AudioRef.new(:audio_track => AudioTrack.new(:user_id => attributes[:user_id], :file => attributes[:file]))
        end
      end
    end
  end

And the spec is now:

it "Should create audio_track and add audio_ref" do
      @audio_track = Fabricate(:audio_track, :user_id => @author.id, :file => File.open("#{Rails.root}/spec/stuff/test.mp3"))
      @feed_item= FeedItem.new(
        :user => @author,
        :message => {:body => Faker::Lorem.sentence(4)},
        :audio_tracks => [
            {:id => @audio_track.id},
            {:user_id => @author.id, :file => File.open("#{Rails.root}/spec/stuff/test.mp3")}
        ]
      )
      @feed_item.save!          
      @feed_item.reload
      @feed_item.audio_refs.length.should be(2)
  end

And it works fine!!! Good luck with your coding)