save! method for referenced attributes in mongoid - ruby-on-rails

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)

Answer 2

Check that audio_refs=() is actually being called, by adding debug output of some kind. My feeling is that your FeedItem.new() call doesn't use the audio_refs=() setter.
Here's the source code of the ActiveRecord::Base#initialize method, taken from APIdock:
# File activerecord/lib/active_record/base.rb, line 1396
def initialize(attributes = nil)
#attributes = attributes_from_column_definition
#attributes_cache = {}
#new_record = true
#readonly = false
#destroyed = false
#marked_for_destruction = false
#previously_changed = {}
#changed_attributes = {}
ensure_proper_type
populate_with_current_scope_attributes
self.attributes = attributes unless attributes.nil?
result = yield self if block_given?
_run_initialize_callbacks
result
end
I don't currently have an environment to test this, but it looks like it's setting the attributes hash directly without going through each attribute's setter. If that's the case, you'll need to call your setter manually.
Actually, I think the fact you're not getting an exception for the number of arguments (binding not set) proves that your setter isn't being called.