elixir ecto naive_datetime 转换错误

Question

在我的 ecto 模型中，我需要在字段中指定:user_timestamp 从 unix_time 转换而来的时间。迁移:

  def change do
    alter table(:operations) do
      add :user_timestamp, :naive_datetime, null: false
    end
  end

我的操作.ex

  schema "operations" do
    field :sum, :float
    field :name, :string
    field :user_timestamp, :naive_datetime

    timestamps()
  end

  def changeset(struct, params \\ %{}) do
    struct
    |> cast(params, [:name, :sum, :user_timestamp])
    |> validate_required([:sum, :user_timestamp])
    |> convert_unix_time_to_ecto
  end

  defp convert_unix_time_to_ecto(changeset) do
    put_change(changeset, :user_timestamp, Ecto.DateTime.from_unix!(changeset.changes.user_timestamp, :seconds) |> Ecto.DateTime.to_naive())
  end

但是当我尝试添加具有 user_timestamp 的要求时，出现错误:

[error] #PID<0.492.0> running MyApp.Endpoint terminated
Server: localhost:4000 (http)
Request: POST /api/v1/operations
** (exit) an exception was raised:
    ** (FunctionClauseError) no function clause matching in Ecto.Type.cast_naive_datetime/1
        (ecto) lib/ecto/type.ex:761: Ecto.Type.cast_naive_datetime(1492722276)
        (ecto) lib/ecto/changeset.ex:523: Ecto.Changeset.cast_field/8
        (ecto) lib/ecto/changeset.ex:482: Ecto.Changeset.process_param/8
        (elixir) lib/enum.ex:1325: Enum."-map_reduce/3-lists^mapfoldl/2-0-"/3
        (elixir) lib/enum.ex:1325: Enum."-map_reduce/3-lists^mapfoldl/2-0-"/3
        (ecto) lib/ecto/changeset.ex:450: Ecto.Changeset.do_cast/7
        (my_app) web/models/operation.ex:25: MyApp.Operation.changeset/2
        (my_app) web/models/operation.ex:32: MyApp.Operation.create_changeset/2
        (my_app) web/controllers/v1/operation_controller.ex:25: MyApp.V1.OperationController.create/2
        (my_app) web/controllers/v1/operation_controller.ex:1: MyApp.V1.OperationController.action/2
        (my_app) web/controllers/v1/operation_controller.ex:1: MyApp.V1.OperationController.phoenix_controller_pipeline/2
        (my_app) lib/my_app/endpoint.ex:1: MyApp.Endpoint.instrument/4
        (my_app) lib/phoenix/router.ex:261: MyApp.Router.dispatch/2
        (my_app) web/router.ex:1: MyApp.Router.do_call/2
        (my_app) lib/my_app/endpoint.ex:1: MyApp.Endpoint.phoenix_pipeline/1
        (my_app) lib/plug/debugger.ex:123: MyApp.Endpoint."call (overridable 3)"/2
        (my_app) lib/my_app/endpoint.ex:1: MyApp.Endpoint.call/2
        (plug) lib/plug/adapters/cowboy/handler.ex:15: Plug.Adapters.Cowboy.Handler.upgrade/4
        (cowboy) /home/mars/phoenix_projects/my_app/deps/cowboy/src/cowboy_protocol.erl:442: :cowboy_protocol.execute/4

如何纠正这个错误？

Answer 1

在您的转换代码有机会运行之前，它在 cast 中失败。

将 :user_timestamp 保留在转换字段列表之外，并使用 put_change 和 validate_required 之前的转换值。

def changeset(struct, params \\ %{}) do

    struct
    |> cast(params, [:name, :sum])
    |> convert_unix_time_to_ecto(params["user_timestamp"])
    |> validate_required([:sum, :user_timestamp])

  end

  defp convert_unix_time_to_ecto(changeset, nil), do: changeset    
  defp convert_unix_time_to_ecto(changeset, timestamp) do
    datetime = 
       timestamp
       |> DateTime.from_unix!(:seconds)
       |> DateTime.to_naive()

    put_change(changeset, :user_timestamp, datetime)
  end