elixir - 一次保存多个 has_many 关联 Phoenix 1.3

Question

我有两个模型:

 defmodule TransactionApi.Messages.Event do
  use Ecto.Schema
  import Ecto.Changeset
  alias TransactionApi.Messages.Event
  alias TransactionApi.Messages.EventDetail

  schema "events" do
    field :city, :string
    field :email, :string
    field :ip, :string
    field :sender, :string
    field :status, :string
    field :subject, :string
    field :template, :string
    field :ts, :utc_datetime
    field :uniq_id, :string
    field :user_agent, :string

    has_many :event_details, EventDetail

    timestamps()
  end

  @doc false
  def changeset(%Event{} = event, attrs) do
    event
    |> cast(attrs, [:sender, :uniq_id, :ts, :template, :subject, :email, :status, :ip, :city, :user_agent])
    |> cast_assoc(:event_details)
    |> validate_required([:sender, :uniq_id, :ts, :subject, :email, :status])
  end
end

defmodule TransactionApi.Messages.EventDetail do
  use Ecto.Schema
  import Ecto.Changeset
  alias TransactionApi.Messages.EventDetail
  alias TransactionApi.Messages.Event


  schema "event_details" do
    field :ts, :utc_datetime
    field :url, :string

    belongs_to :event, Event, foreign_key: :event_id
    timestamps()
  end

  @doc false
  def changeset(%EventDetail{} = event_detail, attrs) do
    event_detail
    |> cast(attrs, [:url, :ts, :event_id])
    |> validate_required([:ts, :event_id])
  end
end

我想在我的 event Controller 中保存事件及其关联的 EventDetail:

  def create(conn, %{"mandrill_events" => event_params}) do
    params = parse_incoming event_params
    with {:ok, %Event{} = event} <- Messages.create_event(params) do
      conn
      |> put_status(:created)
      |> put_resp_header("location", event_path(conn, :show, event))
      |> render("show.json", event: event)
    end
  end

这是我构建的 params map 的样子:

%{      
  city: "Oklahoma City",
  email: "example.webhook@mandrillapp.com",
  event: "open",
  event_details: [
    %{"ts" => #DateTime<2013-04-04 21:31:51Z>, "url" => "http://mandrill.com"},
    %{"ts" => #DateTime<2013-04-04 21:31:51Z>}
  ],
  ip: "127.0.0.1",
  sender: "example.sender@mandrillapp.com",
  status: "sent",
  subject: "This an example webhook message",
  tags: ["webhook-example"],
  template: nil,
  ts: #DateTime<2018-02-12 12:33:48Z>,
  uniq_id: "exampleaaaaaaaaaaaaaaaaaaaaaaaaa",
  user_agent: "Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.6; en-US; rv:1.9.1.8) Gecko/20100317 Postbox/1.1.3"
}

但我的 api 返回错误 : {"errors":{"event_details":[{"event_id":["can't be blank"]},{"event_id":["can't留空"]}]}}

我如何确保关联的 EventDetail 正确地保留了对 Event 表的 foreign_key 引用，这里的“最佳实践”方法是什么？

编辑:

在 Phoenix 1.3 中，他们似乎添加了位于模型上下文中的 create_[table_name] 并处理 changeset 和插入(我认为更改想要将 web 相关部分与应用程序分开，但不确定):

  def create_event(attrs \\ %{}) do
    %Event{}
    |> Event.changeset(attrs)
    |> Repo.insert()
  end

Answer 1

我想出了一种方法来保存包含嵌套关联的 map ，但由于我是 Phoenix 和 Elixir(一般的函数式编程)的新手，我不确定这是正确/最佳实践方法。

%{      
  city: "Oklahoma City",
  email: "example.webhook@mandrillapp.com",
  event: "open",
  event_details: [
    %{"ts" => #DateTime<2013-04-04 21:31:51Z>, "url" => "http://mandrill.com"},
    %{"ts" => #DateTime<2013-04-04 21:31:51Z>}
  ],
  ip: "127.0.0.1",
  sender: "example.sender@mandrillapp.com",
  status: "sent",
  subject: "This an example webhook message",
  tags: ["webhook-example"],
  template: nil,
  ts: #DateTime<2018-02-12 12:33:48Z>,
  uniq_id: "exampleaaaaaaaaaaaaaaaaaaaaaaaaa",
  user_agent: "Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.6; en-US; rv:1.9.1.8) Gecko/20100317 Postbox/1.1.3"
}

event_controller.ex

  def create(conn, %{"mandrill_events" => event_params}) do
    params = parse_incoming event_params
    with {:ok, %Event{} = event} <- Messages.create_event(params) do
      event
      |> Messages.add_event_details(params[:event_details])

      conn
      |> put_status(:created)
      |> put_resp_header("location", event_path(conn, :show, event))
      |> render("show.json", event: event)
    end
  end

然后在我的 Message 上下文中:

  # persist an `event`

  def create_event(%{event: event_params} \\ %{}) do
    %Event{}
    |> Event.changeset(event_params)
    |> Repo.insert()
  end

  # persist a collection of `event_details`

  def add_event_details(%Event{} = event, details) do
    Enum.map(details, fn(event_detail) ->
      event_detail
      |> Map.put("event_id", event.id)
      |> create_event_detail
    end)
  end