Untitled

Create action with a non-persisted record with persisted associations?
class Transaction < ActiveRecord::Base
  # ...
  accepts_nested_attributes_for :user, :shipping_address, :products
  # ...
end

class TransactionsController < ApplicationController
  def new
    @transaction = Transaction.new
  end

  def create
    @transaction = Transaction.new params[:transaction]

    # ...
  end
end

class Transaction < ActiveRecord::Base
  has_many :product_transactions
  has_many :products, :through => :product_transactions
end

class Product < ActiveRecord::Base
  has_many :product_transactions
  has_many :transactions, :through => :product_transactions
end

class ProductTransaction < ActiveRecord::Base
  belongs_to :transaction
  belongs_to :product
end