Using submodel accessor (STI) on parent params for nested forms

Question

i have the following models:

class Order < ApplicationRecord
class Bill < Order
class Preorder < Order

class Detail < ApplicationRecord
class Metric < Detail
class Unit < Detail

the model Order accept nested attributes for Detail, an Order can be a Bill or a Preorder and Detail can be by Unit or by Metric

i'm using jsonb_accessor gem to create additional attributes for Unit and Metric

class Metric < Detail
    jsonb_accessor :data,
      height: :decimal,
      width: :decimal
end

class Unit < Detail
    jsonb_accessor :data,
      quantity: :decimal
end

in my view, i'm using Cocoon gem to generate fields for Unit or Metric

<%= link_to_add_association(I18n.t('activerecord.models.metric.add'), f, :details, data: {association_insertion_node: '#details', association_insertion_method: :append}, :class => "btn btn-success", 
wrap_object: Proc.new { |detail| detail.type = "Metric"; detail = Metric.new }) %>
<%= link_to_add_association(I18n.t('activerecord.models.unit.add'), f, :details, data: {association_insertion_node: '#details', association_insertion_method: :append}, :class => "btn btn-success",
wrap_object: Proc.new { |detail| detail.type = "Unit"; detail = Unit.new }) %>

and in my controller, i have this method to verify the params

def order_params(type)
  if type=="Bill"
    params.require(:bill).permit(:client_id, :type, :delivered, :paid, :total_paid, details_attributes: [:id, :total_price, :type, :data, :service_id, :_destroy])
  elsif type=="Preorder"
    params.require(:preorder).permit(:client_id, :type, :delivered, details_attributes: [:id, :total_price, :type, :data, :service_id, :_destroy])
  end
end

the form works near perfectly, it store all data i put in the form except for :width, :height, :quantity, when i put them in params, it give an error saying that these params do not belong to Detail model and when i put :data instead, the column still empty.

i'm considering, using column directly for parent model Detail instead of using jsonb_accessor, or separate views and controller for each Metric and Unit models but i keep these solutions as last resort because i want to keep the code Dryier and use less columns as possible

nathanvda nathanvda · Accepted Answer · 2017-10-04T12:10:55

Imho the problem is you are using the association details which means that rails is trying to create/save a Detail. Instead you will have to use the respective associations for units and metrics so rails knows to create the correct object which has the respective jsonb_accessors to save correctly.

You can just add the associations in the model:

has_many :metrics 
has_many :units

I get this is possibly not as clean in your UI (if everything is a detail you can just add/list them together). Another alternative is define all possible json-fields in your Detail model (but not entirely sure if that defeats the purpose of using them in the first place).

Using submodel accessor (STI) on parent params for nested forms

1 Answers