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on a Ruby on Rails project I'm trying to access association objects on an ActiveRecord prior to saving everything to the database. class Purchase < ActiveRecord::Base has_many :purchase_items, dependent: :destroy has_many :items, through: :purchase_items validate :item_validation def item_ids=(ids) ids.each do |item_id| purchase_items.build(item_id: item_id) end end private def item_validation items.each do |item| ## Lookup something with the item if item.check_something errors.add :base, "Error message" end end end end If I build out my object like so: purchase = Purchase.new(item_ids: [1, 2, 3]) and try to save it the item_validation method doesn't have the items collection populated yet, so even though items have been set set it doesn't get a chance to call the check_something method on any of them. Is it possible to access the items collection before my purchase model and association models are persisted so that I can run validations against them? If I change my item_validation method to be: def item_validation purchase_items.each do |purchase_item| item = purchase_item.item ## Lookup something with the item if item.something errors.add :base, "Error message" end end end it seems to work the way I want it to, however I find it hard to believe that there is no way to directly access the items collection with rails prior to my purchase and associated records being saved to the database.

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