Could you put that field inside the params before you cast it? Then the type would have all the info it needed.
Adzz
AndrewDryga
This would mean that we would have two fields duplicating type information, add constraints to DB to make sure they are equal and all this just to workaround Ecto limitations. I would rather move type inside payload (which is not ideal for our use cases).
We already have code that makes it possible to have dynamic embeds except you need to call a special “load” function every time schema is returned from DB. This is not very convenient due to Ecto preloads, but works.
0
mathieuprog
@AndrewDryga could you check out the library I published for support for polymorphic embeds?
Would it answer your use case? If not, what would be lacking?
3
lukaszsamson
ElixirLS Core Team
This is slightly offtopic as in my case I needed polymorphic embeds over JSON columns Fix decimal load from JSON serialized map by lukaszsamson · Pull Request #3215 · elixir-ecto/ecto · GitHub
0
thojanssens1
Were you working with a DB that has no JSONB support? Or why did you need to convert to JSON as seen in the code?
0
lukaszsamson
ElixirLS Core Team
I was working with Postgres so JSONB was there. The problem was ecto mapping a single JSON column to one of several structs depending on some other column. Using a simple map serialized to JSON I would lose all ecto goodness like decimals, dates, times, casting, loading, validatins etc.
0
thojanssens1
@lukaszsamson two things
-
I think that the
Ecto.Type.embedded_dumpandEcto.Type.embedded_loadin thoseEnum.reduce_whileare unnecessary, and that represents a lot of code in your Ecto type.
Because you know the schema based on the ‘type’ field (def load(%{@type_field => module_string} = data)), so when loading the data from the DB, you can simply cast those values against the changeset of your schema. And the cast will convert the data to the right elixir data. Or did I miss something? -
I don’t understand why you say off-topic as the library above for example does exactly what you are doing, i.e. picking dynamically an embedded struct based on some ‘type’ field, and store it in some field.
0
lukaszsamson
ElixirLS Core Team
- If I remember correctly the issue with that approach was that dumping my structs as ecto map used default Jason.Encoder protocol implementation for decimals, dates, etc and ecto was then unable to load them correctly (was loosing data or simply crashing)
- You’re right, It’s more on-topic than I initially thought
0
thojanssens1
I don’t see why Ecto could be unable to load data.
I tried playing with datetimes, dates, times, decimals, … to be stored in :map, and all seem to be dumped and loaded back to the right data without issues with Postgres without these encodings/decodings.
Also, do you know what other format can be given to embedded_dump(type, value, format) other than :json?
0
AndrewDryga
Thank you, the library looks nice. It does not fit out needs though as if JSONb column has type information it’s trivial to make it polymorphic without any external libraries (just pattern match on load in specific type).
Our cast is different, in the raw Ecto schema we have a type field and then payload field which should be casted depending on type field value. Which Ecto does not allow as you can’t access type value while casting/dumpin/loading payload field.
0