Rails Nested attributes with check_box loop

Question

So I have a categories model

class Category < ActiveRecord::Base
has_many :provider_categories
has_many :providers, :through => :provider_categories
end

and a provider model

class Provider < ActiveRecord::Base
has_many :provider_categories
has_many :categories, :through => :provider_categories

accepts_nested_attributes_for :provider_categories, :allow_destroy => true
end

here is my provider_category model

class ProviderCategory < ActiveRecord::Base
belongs_to :provider
belongs_to :category
end

I'm trying to create a nested form to include the categories into the provider form

= form_for @provider do |f|
  ...
  -@categories.each.with_index do |category,index|
    =f.fields_for :provider_category, category do |pl|
      =pl.check_box :category_id
      =pl.label category.name
      =pl.hidden_field :provider_id, value: @provider.id

The checkbox is not cooperating when I load the page I get

undefined method `category_id' for #<Category:0x0000010184ff60>

EDIT:

if I change the :category_id to id it works but the html outpuy looks like this

<input name="provider[provider_category][id]" type="hidden" value="0"><input checked="checked" id="provider_provider_category_id" name="provider[provider_category][id]" type="checkbox" value="1">
<label for="provider_provider_category_Acupuncture">Acupuncture</label>
<input id="provider_provider_category_provider_id" name="provider[provider_category][provider_id]" type="hidden" value="1">

EDIT 2:

I ended up using check_box_tag

-@categories.each.with_index do |category|
  =f.fields_for :provider_category, category do |pl|
    .li
      =check_box_tag "provider[provider_category][category_id]", category.id
      =pl.label category.name
      =pl.hidden_field :provider_id, value: @provider.id

Now the html output seems to be correct but it's not saving it. When I select multiple items this is the hash from saving

"provider"=>{"name"=>"Mr. Awesome", "phone"=>"999-999-9999", "email"=>"awesome@awesome.com", "address"=>"awesome land", "provider_category"=>{"category_id"=>"3", "provider_id"=>"1"}}, "commit"=>"Save", "id"=>"1"}

I did select 3 options but only the last one was added to the hash

I also added the provider categories in the strong params of provider controller

params.require(:provider).permit(..., :provider_categories => [:category_id, :provider_id])

Thanks for the help in advance

Answer 1

AS per your model definitions, ProviderCategory has attributes category_id and provider_id. You are getting error as:

undefined method `category_id' for #<Category:0x0000010184ff60>

because instead of passing instance of ProviderCategory, you have passed an instance of Category class. Notice category being passed in

=f.fields_for :provider_category, category do |pl|

and as there is no attribute named category_id in model Category you receive the error.

To resolve that, just update the fields_for method call in your view as below:

=f.fields_for :provider_categories, category.provider_categories.build do |pl|

UPDATE

Also, you would have to update the strong params of ProvidersController so that records for provider_categories are saved correctly in database:

params.require(:provider).permit(..., :provider_categories_attributes => [:category_id, :provider_id])

Use provider_categories_attributes and not provider_categories

UPDATE 2

OP had another problem, for the unchecked category_id, value 0 was being passed and incorrect records with category_id set as 0 were getting created in provider_categories.

Suggested to reject those records by passing reject_if option to accepts_nested_attributes_for method call in Provider model as below:

class Provider < ActiveRecord::Base
  has_many :provider_categories
  has_many :categories, :through => :provider_categories
  accepts_nested_attributes_for :provider_categories, :allow_destroy => true, reject_if: proc { |attributes| attributes['category_id'] == "0" }
end  

Checkbox was not passing the id's of checked categories, suggested to update the checkbox code as below:

=pl.check_box :category_id, {}, category.id, 0