Updating an embedded_schema & general problems understanding Ecto

phoenix_html does work completely without ecto (the integration of ecto comes with the phoenix_ecto package) so you can always set the method you need manually:

from_for form_data, action, [method: :put], fn f -> […] end

Brilliant thank you! I knew there would be a way of doing this, but was trying to tackle it from the Ecto side by forcibly modifying the changesets state or action.

Changing that lets me make the update to the embedded_schema through the form, and some of the subsequent data does indeed update, but certain models/tables don’t.

I think I’ve tied myself up in knots and am fighting Ecto the entire way. Perhaps I should go back to the drawing board and work out what I’m trying to accomplish, and whether I’m making things more complex than they need to be?

Hi @jdumont,

I am kind of having the same issue here. I am building a recipe management app which support recipe versioning. The thing is that my recipe_version schema is immutable, so when a user edits a recipe, it is implicit that he edits the last recipe version but submitting the form will actually create a new version. All the logic (inside my Kitchen context!) is working perfectly.

My data model is as simple as:
Recipe has many RecipeVersion has many {Ingredients, Steps}

I am trying to build a form where the user wouldn’t see the RecipeVersion at all. He would simply edit the Recipe name, the ingredients and steps in place.

I have created an embedded_schema that represents the form parameter but I am running into the same confusion as you.

I was wondering if you found something relevant in your case? Did you simply choose to use the [method: :put] on the form_for tag?

More generally, what are the best practices when you want to decouple your data model from your UI?

Thanks in advance!

@hourliert setting method: :put is completely fine but you can also do this: Ecto.put_meta(embedded_schema, state: :loaded) before wrapping the schema in a changeset and therefore Phoenix<->Ecto will consider it as a PUT. That may be semantically better.

But generally speaking, decoupling your forms (UI representation) from your DB representation is a very good practice. So you are going in the right direction. I also recommend then What’s new in Ecto 2 ebook. It covers this and a couple of other things. The ebook is for 2.0 but almost all of it works just fine on 3.0.

That is awesome!! Thanks for the prompt answer. I was exactly looking for something like this Ecto.put_meta(embedded_schema, state: :loaded). I tried to create and update the __meta__ field on my embedded schema myself in the first place (totally new to Elixir and Phoenix).

I will have a look at the ebook you linked.
Thank you very much again!!!

Hey @josevalim,
I tried your suggestion and I was expecting put_meta to create the meta field on the embedded schema since according to the doc: (Ecto.Schema — Ecto v3.14.0) embedded_schemas don’t have a meta field, but it didn’t seem to work.

Also looking at the code source of Ecto: ecto/lib/ecto.ex at master · elixir-ecto/ecto · GitHub, put_meta won’t match if I am calling it with an embedded_schema.

Error:

** (FunctionClauseError) no function clause matching in Ecto.put_meta/2

    The following arguments were given to Ecto.put_meta/2:

        # 1
        %MyRecipeBox.Kitchen.RecipeCreation{
          cost: nil,
          difficulty: nil,
          id: nil,
          ingredients: [],
          name: nil,
          steps: []
        }

        # 2
        [state: :loaded]

    Attempted function clauses (showing 1 out of 1):

        def put_meta(%{__meta__: meta} = struct, opts)

    (ecto) lib/ecto.ex:560: Ecto.put_meta/2

Did I miss something?

Thanks in advance

Oh, yes, I forgot that embedded do not have a meta field. So yes. In this case, you either need to make it not embdded or pass the method. Sorry for wrong advice!

Oh noo. This solution looked elegant!
In the case I am making this schema not embedded, that would mean that I HAVE to persist it somewhere? I would be back to my initial problem: coupling the database model to the UI right?

I am gonna pass the method to the form for now. If I found something more satisfying, I’ll update this post (or write it somewhere else).

Thanks a lot for the help. Really appreciate it.

No, you don’t have to. You can completely work with them forgetting completely that Ecto.Repo exists.

Oh nice, I think I was confused by the doc.

It makes total sense. Once again, big thanks!