Example of retrieving offerings.

offerings.rb

Spree::LineItem.class_eval do
  def offering
    variant.offering(self.qty)
  end
end

Spree::Variant.class_eval do

  # has_many :volume_prices (viene de la gema)
  has_many :offerings
    
  # Get the right offering for a given Quantity.
  def offering(qty)
    if has_volume_prices?
      self.volume_price(qty).offering
    else
      # If this variant does not have any volume prices, then it should only be associated to one offering.
      offerings.first
    end
  end
  
  def has_volume_prices?
    volume_prices.count > 0
  end
  
end