Question

I have a List model. Lists have embedded Tags (using Mongoid). When a user creates a list, he can specify associated tags via comma separated list in a text field.

How do I store the tags through the List association? Can I do it with accepts_nested_attributes_for :tags on the List model or do I have to pre-process the tags string?

Here’s what I have so far. How do I deal with the tags string, splitting it and storing each tag individually in the embedded tag doc that’s part of list?

List controller:

class ListsController < ApplicationController
  def new
    @list = List.new

    respond_to do |format|
      format.html # new.html.erb
      format.json { render json: @list }
    end
  end

  def create
    list_params = params[:list]
    list_params[:user_id] = current_user.id
    @list = List.new(list_params)
    if @list.save
     redirect_to @list, notice: 'List was successfully created.'
    else
      render action: "new"
    end
  end
end

List creation form

= form_for @list do |f|
  - if @list.errors.any?
    #error_explanation
      %h2= "#{pluralize(@list.errors.count, "error")} prohibited this list from being saved:"
      %ul
        - @list.errors.full_messages.each do |msg|
          %li= msg

  .field
    = f.label :name
    = f.text_field :name
  .field
    = f.label :description
    = f.text_field :description
  .field
    = f.fields_for :tags do |t|
      = t.label :tags
      = t.text_field :name
  .actions
    = f.submit 'Save'

List model

class List
  include Mongoid::Document
  include Mongoid::Timestamps
  field :name
  field :description
  embeds_many :items
  embeds_many :comments
  embeds_many :tags
  belongs_to :user

  accepts_nested_attributes_for :tags

Tag model

class Tag
  include Mongoid::Document
  field :name
  has_one :list
end

Edit based on Geoff’s suggestion

List controller ultimately looked.

 def create
    tags = params[:tags][:name]
    list = params[:list]
    list[:user_id] = current_user.id
    @list = List.new(list)
    tags.gsub("\s","").split(",").each do |tag_name|
      @list.tags.new(:name => tag_name)
    end
    if @list.save
     redirect_to @list, notice: 'List was successfully created.'
    else
      render action: "new"
    end
  end

Answer 1

If I understand you correctly, here’s what I think you want to do:

Your view as it is will display a tag name field for each tag, but there are no associated tags at create time so I assume it just doesn’t show anything.

When using a :has_many, there is a nice little function that will be created for you by rails called List.tag_ids. Since I am not familiar with it, I am assuming the functionality of :embeds_many is a superset of of :has_many. The point of this is that if you can provide some sort of form which gathers the ids, then you’d be done. A set of checkboxes could work, or a multi-select. Here is what checkboxes might look like:

= hidden_field_tag "list[tag_ids][]"
- Tags.all.each do |t|
  = check_box_tag "list[tag_ids][]", t.id, t.list == @list, id: "list_tag_ids_#{t.id}"
  = label_tag "list_tag_ids_#{t.id}", t.name

I asked something similar here:

Rails: How do I transactionally add a has_many association to an existing model?

However, this isn’t what you asked for. You could achieve a form which associates tags by name by using javascript. That would probably be nice, but it would be a bit tricky.

Assuming no javascript, if you are inputting the names as a comma separated list in the view, you will need to parse it in the controller. Similar to this:

View:

label_tag :tags
text_field_tag :tags

Controller:

...
@list = List.new(list_params)
params[:tags].gsub("\s","").split(",").each do |tag_name|
  tag = Tag.find_by_name(tag_name)
  @list.tags << tag if tag
if @list.save
...

None of the solutions I suggested make use of nested attributes. I don’t think they are applicable for you here. They are used when you are trying to update the attributes of the nested model, but you’re just trying to make the association.

I hope that helps.