mathieuprog

mathieuprog

Polymorphic_embed - polymorphic Embeds in Ecto

Hello :waving_hand:

I published a library that brings support for polymorphic/dynamic embeds in Ecto.

Ecto’s embeds_one macro requires a specific schema module to be specified. This library removes this restriction by dynamically determining which schema to use, based on data to be stored (from a form or API) and retrieved (from the data source).

Example use case:

Say you have a Reminder schema. A reminder has a set date and text, but also specific fields whether it is an email reminder or sms reminder. Instead of adding and mixing all the email- and sms-related fields together in the Reminder schema, where one set of fields or the other are null values, you can add a polymorphic embed, only containing the relevant sms or email fields. The polymorphic embed also supports its own changeset validations.

See example code and usage in Readme file :backhand_index_pointing_down:

https://github.com/mathieuprog/polymorphic_embed

Inspired by ecto_poly library.

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mathieuprog

mathieuprog

  • Support for LiveView forms has been added thanks to the quality contribution of Mathias!

  • Support for primary keys has been added

The latter may introduce breaking changes, therefore Polymoprhic Embed version has been bumped to 2.0.0

Migration from 1.x to 2.x is easy:

  • Make sure that every existing polymorphic embedded_schema contains the setting @primary_key false
mathieuprog

mathieuprog

I imagine this is a pretty common need, and that many codebases would either have a schema with sets of null values, or end up having their own custom Ecto type implementations.

This library indeed provides a custom Ecto Type that determines the right embed schema to use, based on params to cast. Nice thing is, you can tell PolymorphicEmbed that the presence of specific params identifies a certain schema – no need for a “type” field in the params:)

In addition to the advantages that a library offers (get rid of boilerplate code in the app, reusable code across projects, bugfixes, …), it comes with some nice features:

  • As mentioned, detect which types to use for the data being cast-ed, based on fields present in the data (no need for a type field in the data)
  • Run changeset validations when a changeset/2 function is present (when absent, the library will introspect the fields to cast)
  • Support for nested polymorphic embeds
  • Support for nested embeds_one/embeds_many embeds
  • Display form inputs for polymorphic embeds in Phoenix templates

Added those features in the Readme file.

mathieuprog

mathieuprog

Version 3.0.0 has been released!

We now encourage the use of polymorphic_embeds_one/2 and polymorphic_embeds_many/2 macros to define your polymorphic embeds.

If you’re curious as to why: a field containing a polymorphic list of embeds defaulted to nil before version 3. To follow embeds_many/3 we should default to []. This can only be done by forcing the :default option of the field/3 to [] (ie we can’t configure this in the Type). I added the new macros in order to set these kind of defaults setting up the field for the polymorphic embeds.

Thanks to Alexandre @Matsa59 for his contribution which led to this update!

Last Post!

munksgaard

munksgaard

This seems to work the first time I select something. But if I then change my selection, it doesn’t actually change anything. Even in my handle_event I’m not seeing the updated selection.

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