Polymorphic Invoice Charges

poly_invoice_example.rb

class Invoice < ActiveRecord::Base
  belongs_to :account
  has_many :charges
end

class Charge < ActiveRecord::Base
  belongs_to :invoice
  belongs_to :chargeable, :polymorphic => true

  delegate :total, to: :chargeable, prefix: true

  scope :ordered_by_date, -> { order(:created_at) }

  def self.line_items_only
    where(:chargeable_type => "LineItem")
  end

  def self.line_items
    LineItem.where(:id => line_items_only.pluck(:chargeable_id))
  end

  def self.interest_charges_only
    where(:chargeable_type => "InterestCharge")
  end

  def self.interest_charges
    InterestCharge.where(:id => interest_charges_only.pluck(:chargeable_id))
  end

  def self.adjustments_only
    where(:chargeable_type => "Adjustment")
  end

  def self.adjustments
    Adjustment.where(:id => adjustments_only.pluck(:chargeable_id))
  end
end

class LineItem < ActiveRecord::Base
  has_one :charge, :as => :chargeable
end

class InterestCharge < ActiveRecord::Base
  has_one :charge, :as => :chargeable
end

class Adjustment < ActiveRecord::Base
  has_one :charge, :as => :chargeable
end