Question

I have 3x models:

class Heuristic < ActiveRecord::Base
  has_many :footnotes
  has_many :references, :through => :footnotes
end

class Reference < ActiveRecord::Base
  has_many :footnotes
  has_many :heuristics, :through => :footnotes
end

class Footnote < ActiveRecord::Base
  belongs_to :reference
  belongs_to :heuristic
end

A join table:

class CreateFootnotes < ActiveRecord::Migration
  def change
    create_table :footnotes do |t|
      t.integer :heuristic_id
      t.integer :reference_id
      t.timestamps
    end
  end
end

A form called from the new reference view:

= form_for @reference do |f|
  .field
    = hidden_field_tag "reference[heuristic_ids][]", nil
    - @heuristics.each do |heuristic|
      = label_tag dom_id(heuristic), heuristic.description
      = check_box_tag "reference[heuristic_ids][]", heuristic.id, @reference.heuristics.include?(heuristic), id: dom_id(heuristic)
  .actions
    = f.submit 'Save'

A references controller:

  def new
    @reference = Reference.new
    @heuristics = Heuristic.all
    respond_to do |format|
      format.html # new.html.erb
    end
  end

  def create
    @reference = Reference.new(params[:reference])
    respond_to do |format|
      if @reference.save
        format.html { redirect_to references_path, notice: 'Reference was successfully created.' }
      else
        format.html { render action: "new" }
      end
    end
  end

When you go to the new reference view, select a heuristic and click Save, I expect this to associate the selected heuristic with the reference, but when you drop into rails console you can see that it has not:

ref = Reference.last
  Reference Load (0.9ms)  SELECT "references".* FROM "references" ORDER BY "references"."id" DESC LIMIT 1
+----+-----+----------+---------+-----------+-------------+
| id |  created_at              | updated_at              |
+----+-----+----------+---------+-----------+-------------+
| 2  |  2012-10-29 11:21:24 UTC | 2012-10-29 11:21:24 UTC |
+----+-----+----------+---------+-----------+-------------+
1 row in set
1.9.2p318 :002 > ref.heuristics
  Heuristic Load (1.0ms)  SELECT "heuristics".* FROM "heuristics" INNER JOIN "footnotes" ON "heuristics"."id" = "footnotes"."heuristic_id" WHERE "footnotes"."reference_id" = 2
 => [] 
1.9.2p318 :003 > Footnote.all
  Footnote Load (0.4ms)  SELECT "footnotes".* FROM "footnotes" 
 => [] 
1.9.2p318 :004 > 

Why is this?

Thanks,

Steven.

BTW, I expected the reference[heuristic_ids][] to dynamically generate the name of each checkbox, but instead the name of each checkbox is the same: reference[heuristic_ids][].

Answer 1

Ensure that the :heuristic_ids (virtual) field is accessible:

attr_accessible :heuristic_ids # in the model. PLURAL!

Then try to do it in the console (with a bang to show any validation error):

> Reference.create!("heuristic_ids"=>["", "2"])

this way you’ll get more information about WHY this doesn’t get saved.