CODEWITHSUNDEEP
ruby-on-railsactiverecord
helpmeplz
helpmeplz

Reputation: 181

Many to many association form with collection_check_boxes results in validation error

I have three models: Course, Category, and Categorisation.

# course.rb
class Course < ApplicationRecord
  has_many :categorisations, foreign_key: "course_id", dependent: :destroy
  has_many :categories, through: :categorisations  
end

#category.rb
class Category < ApplicationRecord
  has_many :categorisations, foreign_key: "category_id", dependent: :destroy
  has_many :courses, through: :categorisations
end

# categorisation.rb
class Categorisation < ApplicationRecord
  belongs_to :course
  belongs_to :category

  validates :course_id, presence: true
  validates :category_id, presence: true
end

Course controller has the following params:

def course_params
  params.require(:course).permit(:name, :prerequisite, :description,
                                 :user_id, :category_ids => [])
end

I'm trying to build the association via the Course form:

<%= form_for @course do |f| %>
  <%= render 'shared/error_messages', object: f.object %>

  <%= f.label :name %>
  <%= f.text_field :name, class: 'form-control' %>

  <%= f.label :prerequisite %>
  <%= f.text_field :prerequisite, class: 'form-control' %>

  <%= f.label :description %>
  <%= f.text_area :description, class: 'form-control' %>

  <%= f.label :category_ids, "Category" %>
  <%= f.collection_check_boxes :category_ids, Category.all, :id, :name, 
                        {}, { multiple: true, class: 'form-control'} %>

  <%= f.submit "Create a new course", class: "btn btn-primary" %>
<% end %>

However when I click submit I get the validation error:

Categorisations is invalid

I'm unsure why this is the case?

Upvotes: 0

Views: 196

Answers (2)

radoAngelov
radoAngelov

Reputation: 714

You're not able to save any entity that relates to Categorization in database because of presence: true action. Firstly, I think it's a better idea to validate :category_id in the schema.rb by category_id null: false. And secondly, are you sure you need the Categorization model? My suggestion is to think of putting a categorizationable.rb file in your yourApp/app/models/concerns folder and after that using its functionality in the existing models. You can read more about concerns here. This technique is really powerful when your models need refactoring.

Upvotes: 1

Deepak Mahakale
Deepak Mahakale

Reputation: 23711

Removing the presence validation on :course_id will fix the issue

class Categorisation < ApplicationRecord
  belongs_to :course
  belongs_to :category

  # validates :course_id, presence: true
  validates :category_id, presence: true
end

Problem:

Course is not saved but due to through association when you associate category with course rails first tries to save categorisation but course_id is not available yet

And this is the reason presence validation fails for course_id

Solution

Removing the validation is just a workaround the actual solution will be something interesting

NOTE: Even I am facing the similar issue a few days back. we have removed validation for now. I will be interested in any better solution

Upvotes: 2

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