Can't preload embedded_schema struct #3238

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1. josevalim commented on Feb 26, 2020

   

   josevalim

   on Feb 26, 2020

   Member

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   Embedded schemas are always loaded when you load entries. You don't have to preload them as they are not in separate tables.
2. josevalim

   closed this as completedon Feb 26, 2020
3. erlandsona commented on Mar 11, 2020

   

   erlandsona

   on Mar 11, 2020

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   @josevalim I'm trying to do the same thing and running into a different error, but what do you mean by...

   Embedded schemas are always loaded when you load entries

   Here's a Command which will be run like Command.run(CreateEncounterQuestionResponse) which just calls things like Repo.transaction and some other book keeping stuff for us.

   defmodule CreateEncounterQuestionResponse do
     typed_embedded_schema do
       field(:response, :string, null: false)
       field(:responded_by_id)
   
       belongs_to(:encounter, Encounter)
     end
   
     def run(params) do
       Multi.new()
       |> Multi.run(:encounter, fn repo, _ ->
         params
         |> repo.preload(
           encounter: [
             questions: from(q in Question, order_by: [q.submitted_at, :desc], limit: 1)
           ]
         )
       end)
       |> Multi.update(:encounter_question, &Question.update/1)
       end)
     end
   end
   

   Then in Question.ex

     @spec update(map()) :: Ecto.Changeset.t(t())
     def update(params) do
       whitelist = [
         :response,
         :responded_by_id,
         :encounter_id
       ]
   
       params.encounter.questions
       |> List.first
       |> cast(params, whitelist)
       |> cast_event(:responded)
       |> validate_required(whitelist)
     end
   

   The idea would be that when this runs the embedded_schema would run a Repo.get with the encounter_id that came in the request and I'd like to use that to get the last unanswered question to provide a response for.

   The error I'm getting is...

   iex(43)> %{"encounter_id" => 167045, "responded_by_id" => "0051C000008oKwNQAU", "response" => "blah stuff"} |> Command.run(CreateEncounterQuestionResponse)
   ** (KeyError) key :__struct__ not found in: %{encounter: #Ecto.Association.NotLoaded<association :encounter is not loaded>, encounter_id: 167045, id: nil, responded_by_id: "0051C000008oKwNQAU", response: "blah stuff"}
       (ecto) lib/ecto/multi.ex:585: Ecto.Multi.apply_operation/5
       (elixir) lib/enum.ex:1940: Enum."-reduce/3-lists^foldl/2-0-"/3
       (ecto) lib/ecto/multi.ex:569: anonymous fn/5 in Ecto.Multi.apply_operations/5
       (ecto_sql) lib/ecto/adapters/sql.ex:903: anonymous fn/3 in Ecto.Adapters.SQL.checkout_or_transaction/4
       (db_connection) lib/db_connection.ex:1427: DBConnection.run_transaction/4
       (ecto) lib/ecto/repo/transaction.ex:20: Ecto.Repo.Transaction.transaction/4
       (ok) lib/ok.ex:29: OK.map/2
       (api) lib/command.ex:44: Command.run/2
   

   Which I'm assuming to mean that an embedded_schema is not a "real" Ecto object of sorts? Or just that I'm not using it like it was designed?
   Weird thing is embedded_schemas are documented / blogged about being used to take in form parameters which is basically what I'm doing here only for JSON post data...
4. erlandsona commented on Mar 11, 2020

   

   erlandsona

   on Mar 11, 2020

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   Scratch that error, I was converting the struct to a map after running apply_action(:insert) on the changeset from the incoming params. I commented out that struct to map conversion and now I'm getting @ZhengQingchen's same MatchError.