Nested field nightmare

Problems: We have a form with structure like below

- user
  - name
  - age
  - estates
    - 1
      - name
      - area
      - size
      - price
    - 2
      - name
      - area
      - size
      - price
    - n....

and we will use simple form for implement view form

  = simple_form_for :user do |f|
    = f.input :name
    = f.input :age

but I want to save estates to json data of user without model Estate. And I must validate input of all fields of Estate object, keep data on input when submit false. I thought about nested fields without model.

Solution: Create an ruby object:

class Estate
  include ActiveModel::Validations
  # include this calling method .valid? for instance of Estate
end

  10.times { @estates << Estate.new }

  # form.html.slim
  = simple_form_for :user do |f|
    = f.input :name
    = f.input :age

    @estates.each do |estate|
      = render partial: 'estate', locals: { f: f, estate: estate }

  # _estate.html.slim
  = fields_for 'estate[]', estate do |e|
    = e.input :name
    = e.input :size

Now, when submit form we will see params:

params: { user: {
            name: 'xxx',
            age: 'xxx',
            estates: {
              0 => { name: 'xxx', size: 'xxx'},
              1 => { name: 'xxx', size: 'xxx'},
              2 => { name: 'xxx', size: 'xxx'}....
            } }
        }

same as nested field with model. Of course, when we submit failed, all input of estates will be keep on form.( remember assign id for every Estate object )

References:

Create Multiple Objects From Single Form in Rails