nested form in Activeadmin with dropdown selection - Ruby on Rails

Question

I have the next database design:

A order can have a size and a size can be in many orders .

For example:

Order 1 has a size attribute equal to medium

Order 2 has a size attribute equal to medium

I want to be able to select a size when I create a Order in active admin.

Order model:

class Order < ApplicationRecord
  has_one :order_size
  accepts_nested_attributes_for :order_size, :allow_destroy => true
end

Order size model:

class OrderSize < ApplicationRecord
  belongs_to :orders
end

Also, OrderSize table has to have a order_id column?

I don't know if the models are rights but activeadmin is giving me this error:

undefined method `order_id' for #<Order:0x007fb980e34b80>

My activeadmin models

Order Size:

ActiveAdmin.register OrderSize do
  permit_params :name
end

Order:

ActiveAdmin.register Order do
  permit_params :due_date, :comments, :approved, :order_size_id,
                order_size_attributes: [:id, :name,:_destroy]

  form do |f|
    f.inputs "Admin Details" do
      f.input :due_date
      f.input :order_size
      f.input :comments
      f.input :approved
    end
    f.actions
  end

end

Answer 1

I don't know if the models are rights but activeadmin is giving me this error:

undefined method `order_id' for Order:0x007fb980e34b80

Yes, Rails expects a foreign_key(order_id) of associated model(order) for ObjectRelationalMapping(ORM) to communicate with RDBMS . Create a migration for order_id and run rake db:migrate to resolve the problem.

Also the association name for belongs_to or has_one should be singular .

class OrderSize < ApplicationRecord
  belongs_to :order
end

Additionally, you shouldn't have order_size_id in orders as the association is has_one :order_size . Instead as I pointed out above, you should have order_id in order_sizes .