RoR: NoMethodError when executing delete_all for a has_many relationship

Question

My classes are as follows, with Customer inheriting from User using the single-table inheritance approach. User has attributes name and email while Order has destination.

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Answer 1

It seems you have no inverse associations and Rails fails to resolve the order's customer when updating the cached counters. Try this:

class Customer < User
  has_many :orders, inverse_of: :customer
end

class Order < ActiveRecord::Base
  belongs_to :customer, inverse_of: :orders
end