cocoon number of nested fields increasing after validation fail

Question

Rails 4.2.1, Ruby 2.2.1 Gems: simple_form, cocoon

Here are the models with relations:

class User < ActiveRecord::Base
  has_many :galleries, dependent: :destroy
  accepts_nested_attributes_for :galleries, reject_if: :all_blank, allow_destroy: true
  validates_presence_of :name
end

class Gallery < ActiveRecord::Base
  belongs_to :user
  has_many :photos, dependent: :destroy

  accepts_nested_attributes_for :photos, reject_if: :all_blank, allow_destroy: true

  after_initialize :make_photos

  private

  def make_photos
    6.times { photos.build }
  end
end

class Photo < ActiveRecord::Base
  belongs_to :gallery

  validates :size, presence: true, numericality: { only_integer: true }
end

Gallery should have exactly 6 photos, that's why I used after_initialize callback to build 6 photo objects.

views:

user form

  .form-inputs
    = f.simple_fields_for :galleries do |gallery|
      = render 'gallery_fields', f: gallery
    .links
      = link_to_add_association 'add gallery', f, :galleries

gallery fields

.nested-fields
  = f.simple_fields_for :photos do |photo|
    = render 'photo_fields', f: photo
= link_to_remove_association 'remove photos', f
br

photos fields

.nested-fields
  = f.input :size

If I type correct value in first input and incorrect in others after validation fail the result will be 1 input with filled correct value + 6 empty input fields and so on.

How do I avoid it? I always need to build 6 photos per gallery, if User decided to have one.

I pushed sample app on github, so you can reproduce the problem https://github.com/gabyshev/cocoon_example_increasing_number_of_fields

Answer 1

I think the problem is because you have 1 valid associated record, and you are still building 6 records, after object is initialized! To avoid you can do following:

  def make_photos
    photos.size.upto(6).each { photos.build }
  end