迭代哈希值以保存嵌套属性

Question

I have a hash of hashes that I obtain from the params. Looking like this:

{"0"=>{"product_attribute_id"=>"4"}, "1"=>{"product_attribute_id"=>"7"}}

now essentially what I want to do is something like this:

  class Cart < ApplicationRecord
  has_many :line_items, dependent: :destroy

  def add_product(product_id, instruction, attributes)
    current_item = line_items.find_by(product_id: product_id)
    if current_item
      current_item.quantity += 1
    else
      current_item = line_items.build(product_id: product_id, instruction: instruction)
      attributes.each do |key, value|
        current_item.line_item_attributes.build(product_attribute_id: value['product_attribute_id'])
      end
    end
    current_item
  end

but for some reason this doesn't seem to work

Answer 1

Just fyi, assuming you are using the Rails' build method used in active model associations, build will not save to database.

See http://api.rubyonrails.org/classes/ActiveRecord/Associations/ClassMethods.html It reads:

build_association(attributes = {}) Returns a new object of the associated type that has been instantiated with attributes and linked to this object through a foreign key, but has not yet been saved.