Nested attributes validation fails on create new record because parent id has not yet been set

The problem:

class Item < ActiveRecord::Base
    has_many :related_items
  accepts_nested_attributes_for :related_items
end

class RelatedItem
  validates :order, presence: true
end

This works fine if you’re updating an existing item, but when creating a new item, the related item order validation will fail because the item has not been saved yet, and thus has no assigned id.

Using :inverse_of will solve this problem:

class Item < ActiveRecord::Base
  has_many :related_items, inverse_of: :item
  accepts_nested_attributes_for :related_items
end

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Apr 22, 2013

Nested attributes validation fails on create new record because parent id has not yet been set