mongoid save embedded documents

Question

I'm trying to build up on the following tutorial from railscast: http://railscasts.com/episodes/196-nested-model-form-part-1

I'm trying to make everything work with mongodb and mongoid.

the scenario is: I want to creates events linked to a location. Each events (dance class) contains many lessons. So I thought that an embedded relationship would be perfect.

Here are my models

model Lesson

class Lesson
  include Mongoid::Document
  include Mongoid::Slug
  field :name, :type => String

  embedded_in :event

  slug :name
end

model Event

class Event
  include Mongoid::Document
  include Mongoid::Slug
  include Mongoid::Timestamps
  include Mongoid::MultiParameterAttributes

  field :name, :type => String
  field :description, :type => String
  field :date, :type => DateTime

  validates_presence_of :name

  has_one :venue
  referenced_in :venue
  embeds_many :lessons

  slug :name 
end

model Venue

class Venue
  include Mongoid::Document
  include Mongoid::Slug
  include Mongoid::Timestamps
  include Mongoid::MultiParameterAttributes


  field :name, :type => String
  field :location, :type => String

  validates_presence_of :name, :location

  belongs_to :event

  slug :name
end

event controller

def create
  @event = Event.new(params[:event])
    if @event.save
    flash[:notice] = 'Event was successfully created.'
  end
 respond_with(@Event, :location => events_url)
end

def update
  # @event = Event.find(params[:id])
   @event = Event.find_by_slug(params[:id])
   if @event.update_attributes(params[:event])
      flash[:notice] = "Event was succesfully updated"
    end
  respond_with(@event)
end

Then I have my Event view where I can create events and link it to a Venue. But I'd like to be abe to create the lessons from the Event view/model.

so I used the fields_for to generate a field linked to the Lessons model.

= form_for @event do |f|
  .field
    = f.label :name
    %br/
    = f.text_field :name
  .field
    = f.label :description
    %br/
    = f.text_area :description
  .field
    = f.label :venue_id
    %br/
    = f.collection_select :venue_id, Venue.all, :id, :name
  .field
    = f.label :date
    %br/
    = f.datetime_select :date
  %h3 Add a Class
    = f.fields_for :lessons do |builder|
     = render "lesson_fields", :f => builder
 .actions
    = f.submit 'Save'

When I create or edit a new event I get an error message:

undefined method `extract_id' for "test":String

But the request parameter message on the error page shows my lessons value in the Event document.

"lessons"=>{"name"=>"test name lesson"}

When I remove the fields_for line, everything works fine. But then i don't know how to save the value for the nested documents.

can you post the exact code you use to create the Event, including parameters? extract_id is a Method in Mongoid::Criteria btw. — Tilo
I've edited the question with the controller info (create and update) where the action fails. I have also corrected the field name as you mentionned, but it's still not working :( — Yannick Schall
quick question, should the embedded document have an id? "lessons"=>{"name"=>"test name lesson", lesson_id="xxxxxxxxxxxx"} — Yannick Schall
the embedded lessons array will contain an id for each lesson in the embedded collection -- assigned by Mongodb/Mongoid — Tilo
so if i get this on the error page, is it normal? gist.github.com/1361107 — Yannick Schall

Mada Aryakusumah Mada Aryakusumah · Accepted Answer · 2013-07-14T10:21:41

I have same problem with embeds_many, but when i try change to has_many. It works!. Maybe you can try too.