Question

I am trying to implement a checkbox in a nested form.

I have 3 models: Subjects, Lessons and Groups.
A Subjects has many lessons and each lesson has and belongs to many groups.

To put it in another way:
I have Subjects as the parent class, Lessons as the child class and Groups as the “grandchild” class.

In the Subjects form, I have allowed the creation of 3 lessons in a nested form.
I have already created groups before hand and right now, I want to create HABTM checkboxes for groups in each lesson but I am facing some trouble trying to send the parameters in Rails.

The main difference in the parameters is that currently I am sending

"lesson"=>{"group_ids"=>["105", "106", "107"]} 

on its own. However what I want is for the group_ids to be sent for each individual lessons of the subject as such:

"lessons_attributes"=>{"0"=>{"lesson_type"=>"Lecture", 
                             "id"=>"348",
                             "group_ids"=>["37", "38", "39", "40", "41", "42", "131"]}.

To elaborate,
this is the current parameters in full that I am sending:

Parameters: {"utf8"=>"✓", "authenticity_token"=>"7r9g2d4lmiSyNZ60i8uos9m1shxVwb0Ly23Tkrshv8w=", "subject"=>{"subject_code"=>"", "subject_name"=>"", 
                   "lessons_attributes"=>{"0"=>{"lesson_type"=>"Lecture", "id"=>"348"}, 
                                          "1"=>{"lesson_type"=>"Tutorial","id"=>"349"}, 
                                          "2"=>{"lesson_type"=>"Laboratory","id"=>"350"}}, 
                                          "remarks"=>""},
                                          "lesson"=>{"group_ids"=>["105", "106", "107"]}, "commit"=>"Update Subject", "id"=>"166"}

The parameters which I want to send however is as such:

Parameters: {"utf8"=>"✓", "authenticity_token"=>"7r9g2d4lmiSyNZ60i8uos9m1shxVwb0Ly23Tkrshv8w=", "subject"=>{"subject_code"=>"", "subject_name"=>"", 
                 "lessons_attributes"=>{"0"=>{"lesson_type"=>"Lecture", "id"=>"348","group_ids"=>["37", "38", "39", "40", "41", "42", "131"]}, 
                                        "1"=>{"lesson_type"=>"Tutorial","id"=>"349", 
                                              "group_ids"=>["37", "38", "39", "40", "41", "42", "131"], 
                                        "2"=>{"lesson_type"=>"Laboratory","id"=>"350",
                                              "group_ids"=>["37", "38", "39", "40", "41", "42", "131"]}}, "remarks"=>""}, "commit"=>"Update Subject", "id"=>"166"}

I am not sending the parameters right and the problem lies in: `

<%= check_box_tag "lesson[group_ids][]", group.id, f.object.groups.include?(group) , id: "lesson_group_ids_#{group.id}"%>`

And particularly that for my checkbox I am implementing this: lesson[group_ids][].

I have also tried lesson_attributes[group_ids][].
But similarly I could not get the HABTM relationships to save. I am not sure as to what I could do such that the groups saves for each lesson. Any help would be appreciated.

These are the relevant codes:

<%= form_for(@subject) do |f| %>

  <div class="field">
    <%= f.label :subject_name %><br />
    <%= f.text_field :subject_name %>
  </div>

  <div>
    <%= f.fields_for :lessons do |lesson| %>
     <%= render "lesson_fields", :f => lesson %>
    <% end %>
  </div>

  <div class="actions">
    <%= f.submit %>
  </div>

<% end %>

In _lesson_fields.html.erb, I have:

<div class="field">
    <%= f.label :lesson_type %><br />
    <%= f.text_field :lesson_type,:readonly => true %>
  </div>

  <div>
  <% Group.all.each do |group|%>
   <div>
      <%= check_box_tag "lesson[group_ids][]", group.id, f.object.groups.include?(group) , id: "lesson_group_ids_#{group.id}"%>       
     <%= group.group_index %>  
   </div>
  <%end%>
  </div>

And for the models

The relevant models:

class Subject < ActiveRecord::Base
  attr_accessible :lessons_attributes
  has_many :lessons
end

class Lesson < ActiveRecord::Base
  belongs_to :subject
  has_and_belongs_to_many :groups
end

class Group < ActiveRecord::Base
  has_and_belongs_to_many :lessons 
end

Answer 1

I beleive you’re missing an index after ‘lesson’ on the name of the checkbox tag (as in ‘lesson[0][group_ids][]’. You can either add that manually, or you may be able to do something with fields_for. I tend to do what you’re doing – loop through all Groups and show them all, decide if they are checked with a boolean test.