【Elixir]在Ecto中使用虚拟字段以及数据查询

在Ecto中使用虚拟字段以及数据查询

defmodule Friends.Person do
  use Ecto.Schema
  import Ecto.Query

  schema "people" do
    field(:first_name, :string)
    field(:last_name, :string)
    field(:age, :integer, default: 0)
    field(:create_time, :utc_datetime_usec)
    field(:create_time_str, :string, virtual: true)
  end

  def changeset(person, params \\ %{}) do
    person
    |> Ecto.Changeset.cast(params, [:first_name, :last_name, :age, :create_time])
    |> Ecto.Changeset.validate_required([:first_name, :last_name], message: "参数不能为空")
  end

  def find_by_id(id) do
    person = Friends.Repo.get!(Friends.Person, id)
    {_, time_str} = Friends.DatetimeFormat.format_datetime_local!(person.create_time)

    Map.put(person, :create_time_str, time_str)
  end

  def find_by_id_merge() do
    Friends.Repo.all(
      from(p in Friends.Person,
        select_merge: %{
          create_time_str: fragment("TO_CHAR(create_time, 'YYYY-MM-DD HH24:MI:SS')")
        }
      )
    )
  end
end