Untitled

## Model
class ContainerCharge < ShipmentCharge
  belongs_to :container
end

class Container < ActiveRecord::Base
  has_many :container_charges
end

class HandlingContainerCharge < ContainerCharge
end
class ShippingContainerCharge < ContainerCharge
end

## Controller

#Please assume here that this container has many Handling and Shipping charges
container.container_charges # <- doesn't return the handling and shipping charges,
#only instances of the the super class ContainerCharge