Implementing Polymorphic Embeds using Ecto in Elixir

Dan Schultzer discusses his approach to handling polymorphic embeds in Ecto for Phoenix applications. He articulates how he extended the native Ecto embed functionality to allow for polymorphic embeds, which help manage semi-arbitrary data in embedded schemas within forms, without the need for database persistence. The article provides code examples demonstrating how to set up an embedded schema with polymorphic embeds and the accompanying changeset definitions. The use of a parameterized type, a feature offered by Ecto, is introduced to achieve this functionality. By using `PolymorphicEmbed.cast_polymorphic_embed/3` function within the changeset, it manipulates the changeset types to behave like regular hardcoded embedded fields when casting the polymorphic embed. The content also provides insight into how to implement use within Phoenix forms, mentioning the necessity of the `:if` attribute in the form to accommodate different metadata fields of the polymorphic embed. Schultzer underlines that changesets should always be run through the defined `changeset/2` function to ensure the polymorphic embeds are appropriately set.