Change in the mix phx.gen.schema generated file

Phoenix Forum Questions / Help
1

Phoenix 1.3.0 generated the following something.ex file when I ran mix phx.gen.schema MyContext.Something somethings name whatever.

defmodule MyApp.MyContext.Something do
  use Ecto.Schema
  import Ecto.Changeset
  alias MyApp.MyContext.Something


  schema "somethings" do
    field :name, :string
    field :whatever, :string

    timestamps()
  end

  @doc false
  def changeset(%Something{} = something, attrs) do
    something
    |> cast(attrs, [:name, :whatever])
    |> validate_required([:name, :whatever])
  end
end

But now Phoenix 1.3.2 generates the following something.ex file when I ran the same command.

defmodule MyApp.MyContext.Something do
  use Ecto.Schema
  import Ecto.Changeset


  schema "somethings" do
    field :name, :string
    field :whatever, :string

    timestamps()
  end

  @doc false
  def changeset(something, attrs) do
    something
    |> cast(attrs, [:name, :whatever])
    |> validate_required([:name, :whatever])
  end
end

tldr; The Alias for MyContext.Something is removed and the first argument inside changeset function changes from %Something{} = something to something.

When I tested to insert some values from the iex, it behaved like previously, but I wonder what changed under the hood and why?

I’d love if @chrismccord or someone else from the Phoenix core team tell me, how and why this change was made.

Thank you!

2

I’m not in any way related to the core team, but the only thing changed in your code snippet is that a pattern match on %MyContext.Something{} in changeset/2 has been removed.

1 Like
3

The new way can accept plain maps to cast and verify them. The older ones needed a strict to generate proper changeset.

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4

Not quite plain maps, but a tuple of plain maps {data :: map, types :: map}.

https://hexdocs.pm/ecto/Ecto.Changeset.html#cast/4

From the docs

iex> data = %{title: "hello"}
iex> types = %{title: :string}
iex> changeset = cast({data, types}, %{title: "world"}, [:title])
iex> apply_changes(changeset)
%{title: "world"}

So now changeset can be used like so

# ...
{old_data, types}
|> Something.changeset(attrs)
# ...
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