Ecto embed timestamps inserted_at updated

Phoenix Forum Questions / Help
,
1

So I have this embed structure:

defmodule MyApp.Struct do
  use Ecto.Schema
  import Ecto.Changeset
  
  @primary_key false
  @derive Jason.Encoder
  embedded_schema do
    field(:name, :string)
    field(:completed_at, :utc_datetime)
    timestamps()
  end

end

I wanted to have inserted_at and updated_at fields set, so I added the timestamps() line.

It seems like the updated_at value works correctly, but the inserted_at keeps on being updated on each update, which is not what I want.

Here’s how I do the update, from the Holder struct:

defmodule MyApp.Holder do
  schema "holder" do
    embeds_one(:struct, MyApp.Struct, on_replace: :delete)
  end

  def save_struct(holder, struct_params) do
    holder
    |> change()
    |> put_embed(
      :struct,
      MyApp.Holder.changeset(
        holder.struct || %MyApp.Holder{},
        struct_params
      )
    )
    |> Repo.update()
  end

end

I thought this would have to do with put_embed vs cast_embed, but with cast_embed, I need to pass all struct_params, which is not what I want.

So I went for a manual solution:

    field(:inserted_at, :utc_datetime)
    field(:updated_at, :utc_datetime)

  def changeset(struct, params) do
    struct
    |> cast(params, [:name, :completed_at])
    |> cast(%{inserted_at: struct.inserted_at || Timex.now(), updated_at: Timex.now()}, [:inserted_at, :updated_at])
  end

But this is much less elegant.

What am I doing wrong? Or is this because of the embed thing?

Thanks

2

Hi,

What I experienced so far inserted_at and updated_at are reserved by timestamps(). Try to use something else for those fields in the migration like last_modified last_inserted. Then you can naivedatetime for the fields directly in the database or have a look here on other options.

https://hexdocs.pm/ecto/Ecto.Schema.html#module-types-and-casting

3

I may have been unclear.

I’d rather use timestamps() than custom inserted_at and updated_at, but it doesn’t behave expectingly and that’s why I’m asking.

4

I’m Elixir beginner and haven’t used this embed Ecto stuff but this look wrong to me

MyApp.Holder.changeset(
        holder.struct || %MyApp.Holder{},
        struct_params
      )

Isn’t holder.struct type of MyApp.Struct? This should be holder.struct || %MyApp.Struct{} right? Then maybe MyApp.Holder.changeset should be MyApp.Struct.changeset.I think you could also use Ecto.Changeset.change instead of calling structs changeset directly.

5

Yes you are correct.

I did change the name of the objects to un-specify those, and I might have confused myself.

Unfortunately it seems like I can’t edit it anymore. :frowning: