gistfile1.rb

# this one does NOT work
params[:wine] = {:bulk_price_per_dozen => 50}
@wine = Wine.new(params[:wine])

# this one ALSO does NOT work
@wine = current_seller.wines.build(params[:wine])

# this one does work
@wine = current_seller.wines.build
@wine.attributes = params[:wine]


Class Wine < ActiveRecord::Base
  belongs_to :seller
  
  before_validation :do_something_with_seller

  def do_something_with_seller
    # Here you have seller available
  end
end