Elixir 无法对错误消息进行编码

我使用phoenix作为JSON API。我的一个模型如下所示，除非唯一约束检查失败，否则该模型运行良好。发生这种情况时，我会出现以下错误：

(Poison.EncodeError) unable to encode value: {"Email address is already registered", []}

型号：

defmodule MyApp.Registration do
  use MyApp.Web, :model

  @derive {Poison.Encoder, only: [:name, :email, :category]}
  schema "registrations" do
    field :name, :string
    field :category, :string
    field :email, :string

    timestamps
  end

  def changeset(model, params \\ :empty) do
    model
    |> cast(params, ~w(name email category), [])
    |> validate_length(:name, min: 1, max: 240)
    |> unique_constraint(:email, message: "Email address is already registered")
  end

end

def create(conn, registration_params) do
  changeset = Registration.changeset(%Registration{}, registration_params)
  case  Repo.insert(changeset) do
    {:ok, _registration} ->
      # Success 
    {:error, error} ->
      conn
      |> put_status(:unprocessable_entity)
      |> render(MyApp.ErrorView, "generic.json", error: error)
  end
end

def render("generic.json", error) do
  error
end

def translate_errors(changeset) do
  Ecto.Changeset.traverse_errors(changeset, &translate_error/1)
end

def render("error.json", %{changeset: changeset}) do
  # When encoded, the changeset returns its errors
  # as a JSON object. So we just pass it forward.
  %{errors: translate_errors(changeset)}
end

def create(conn, registration_params) do
  changeset = Registration.changeset(%Registration{}, registration_params)
  case  Repo.insert(changeset) do
    {:ok, _registration} ->
      # Success 
    {:error, changeset} ->
      conn
      |> put_status(:unprocessable_entity)
      |> render(MyApp.ErrorView, "error.json", changeset: changeset)
  end
end

defmodule MyAppWeb.ErrorHelpers do
  def translate_error({msg, opts}) do
    if count = opts[:count] do
      Gettext.dngettext(MyAppWeb.Gettext, "errors", msg, msg, count, opts)
    else
      Gettext.dgettext(MyAppWeb.Gettext, "errors", msg, opts)
    end
  end
end

控制器：

defmodule MyApp.Registration do
  use MyApp.Web, :model

  @derive {Poison.Encoder, only: [:name, :email, :category]}
  schema "registrations" do
    field :name, :string
    field :category, :string
    field :email, :string

    timestamps
  end

  def changeset(model, params \\ :empty) do
    model
    |> cast(params, ~w(name email category), [])
    |> validate_length(:name, min: 1, max: 240)
    |> unique_constraint(:email, message: "Email address is already registered")
  end

end

def create(conn, registration_params) do
  changeset = Registration.changeset(%Registration{}, registration_params)
  case  Repo.insert(changeset) do
    {:ok, _registration} ->
      # Success 
    {:error, error} ->
      conn
      |> put_status(:unprocessable_entity)
      |> render(MyApp.ErrorView, "generic.json", error: error)
  end
end

def render("generic.json", error) do
  error
end

def translate_errors(changeset) do
  Ecto.Changeset.traverse_errors(changeset, &translate_error/1)
end

def render("error.json", %{changeset: changeset}) do
  # When encoded, the changeset returns its errors
  # as a JSON object. So we just pass it forward.
  %{errors: translate_errors(changeset)}
end

def create(conn, registration_params) do
  changeset = Registration.changeset(%Registration{}, registration_params)
  case  Repo.insert(changeset) do
    {:ok, _registration} ->
      # Success 
    {:error, changeset} ->
      conn
      |> put_status(:unprocessable_entity)
      |> render(MyApp.ErrorView, "error.json", changeset: changeset)
  end
end

defmodule MyAppWeb.ErrorHelpers do
  def translate_error({msg, opts}) do
    if count = opts[:count] do
      Gettext.dngettext(MyAppWeb.Gettext, "errors", msg, msg, count, opts)
    else
      Gettext.dgettext(MyAppWeb.Gettext, "errors", msg, opts)
    end
  end
end

查看：

defmodule MyApp.Registration do
  use MyApp.Web, :model

  @derive {Poison.Encoder, only: [:name, :email, :category]}
  schema "registrations" do
    field :name, :string
    field :category, :string
    field :email, :string

    timestamps
  end

  def changeset(model, params \\ :empty) do
    model
    |> cast(params, ~w(name email category), [])
    |> validate_length(:name, min: 1, max: 240)
    |> unique_constraint(:email, message: "Email address is already registered")
  end

end

def create(conn, registration_params) do
  changeset = Registration.changeset(%Registration{}, registration_params)
  case  Repo.insert(changeset) do
    {:ok, _registration} ->
      # Success 
    {:error, error} ->
      conn
      |> put_status(:unprocessable_entity)
      |> render(MyApp.ErrorView, "generic.json", error: error)
  end
end

def render("generic.json", error) do
  error
end

def translate_errors(changeset) do
  Ecto.Changeset.traverse_errors(changeset, &translate_error/1)
end

def render("error.json", %{changeset: changeset}) do
  # When encoded, the changeset returns its errors
  # as a JSON object. So we just pass it forward.
  %{errors: translate_errors(changeset)}
end

def create(conn, registration_params) do
  changeset = Registration.changeset(%Registration{}, registration_params)
  case  Repo.insert(changeset) do
    {:ok, _registration} ->
      # Success 
    {:error, changeset} ->
      conn
      |> put_status(:unprocessable_entity)
      |> render(MyApp.ErrorView, "error.json", changeset: changeset)
  end
end

defmodule MyAppWeb.ErrorHelpers do
  def translate_error({msg, opts}) do
    if count = opts[:count] do
      Gettext.dngettext(MyAppWeb.Gettext, "errors", msg, msg, count, opts)
    else
      Gettext.dgettext(MyAppWeb.Gettext, "errors", msg, opts)
    end
  end
end

我想我可能需要以某种方式将错误消息添加到

Poison.Encoder中，仅限于：[]

列表，但我不确定如何做到这一点

编辑

---

我应该澄清，如果我没有指定自定义错误，我仍然会收到与通用错误消息相同的错误。

我认为如果使用

mix phoenix.gen.json

，这是自动完成的，但是变更集错误需要转换为json

查看：

defmodule MyApp.Registration do
  use MyApp.Web, :model

  @derive {Poison.Encoder, only: [:name, :email, :category]}
  schema "registrations" do
    field :name, :string
    field :category, :string
    field :email, :string

    timestamps
  end

  def changeset(model, params \\ :empty) do
    model
    |> cast(params, ~w(name email category), [])
    |> validate_length(:name, min: 1, max: 240)
    |> unique_constraint(:email, message: "Email address is already registered")
  end

end

def create(conn, registration_params) do
  changeset = Registration.changeset(%Registration{}, registration_params)
  case  Repo.insert(changeset) do
    {:ok, _registration} ->
      # Success 
    {:error, error} ->
      conn
      |> put_status(:unprocessable_entity)
      |> render(MyApp.ErrorView, "generic.json", error: error)
  end
end

def render("generic.json", error) do
  error
end

def translate_errors(changeset) do
  Ecto.Changeset.traverse_errors(changeset, &translate_error/1)
end

def render("error.json", %{changeset: changeset}) do
  # When encoded, the changeset returns its errors
  # as a JSON object. So we just pass it forward.
  %{errors: translate_errors(changeset)}
end

def create(conn, registration_params) do
  changeset = Registration.changeset(%Registration{}, registration_params)
  case  Repo.insert(changeset) do
    {:ok, _registration} ->
      # Success 
    {:error, changeset} ->
      conn
      |> put_status(:unprocessable_entity)
      |> render(MyApp.ErrorView, "error.json", changeset: changeset)
  end
end

defmodule MyAppWeb.ErrorHelpers do
  def translate_error({msg, opts}) do
    if count = opts[:count] do
      Gettext.dngettext(MyAppWeb.Gettext, "errors", msg, msg, count, opts)
    else
      Gettext.dgettext(MyAppWeb.Gettext, "errors", msg, opts)
    end
  end
end

控制器：

defmodule MyApp.Registration do
  use MyApp.Web, :model

  @derive {Poison.Encoder, only: [:name, :email, :category]}
  schema "registrations" do
    field :name, :string
    field :category, :string
    field :email, :string

    timestamps
  end

  def changeset(model, params \\ :empty) do
    model
    |> cast(params, ~w(name email category), [])
    |> validate_length(:name, min: 1, max: 240)
    |> unique_constraint(:email, message: "Email address is already registered")
  end

end

def create(conn, registration_params) do
  changeset = Registration.changeset(%Registration{}, registration_params)
  case  Repo.insert(changeset) do
    {:ok, _registration} ->
      # Success 
    {:error, error} ->
      conn
      |> put_status(:unprocessable_entity)
      |> render(MyApp.ErrorView, "generic.json", error: error)
  end
end

def render("generic.json", error) do
  error
end

def translate_errors(changeset) do
  Ecto.Changeset.traverse_errors(changeset, &translate_error/1)
end

def render("error.json", %{changeset: changeset}) do
  # When encoded, the changeset returns its errors
  # as a JSON object. So we just pass it forward.
  %{errors: translate_errors(changeset)}
end

def create(conn, registration_params) do
  changeset = Registration.changeset(%Registration{}, registration_params)
  case  Repo.insert(changeset) do
    {:ok, _registration} ->
      # Success 
    {:error, changeset} ->
      conn
      |> put_status(:unprocessable_entity)
      |> render(MyApp.ErrorView, "error.json", changeset: changeset)
  end
end

defmodule MyAppWeb.ErrorHelpers do
  def translate_error({msg, opts}) do
    if count = opts[:count] do
      Gettext.dngettext(MyAppWeb.Gettext, "errors", msg, msg, count, opts)
    else
      Gettext.dgettext(MyAppWeb.Gettext, "errors", msg, opts)
    end
  end
end

编辑

添加

translate\u错误\1

函数定义。这包含在名为

MyApp.ErrorHelpers

的模块中，该模块导入到

web/my_app.ex

或

lib/my_app\u web.ex

中的

视图

函数定义中，具体取决于您的phoenix版本

lib/my\u app\u web/views/error\u helpers.ex

：

defmodule MyApp.Registration do
  use MyApp.Web, :model

  @derive {Poison.Encoder, only: [:name, :email, :category]}
  schema "registrations" do
    field :name, :string
    field :category, :string
    field :email, :string

    timestamps
  end

  def changeset(model, params \\ :empty) do
    model
    |> cast(params, ~w(name email category), [])
    |> validate_length(:name, min: 1, max: 240)
    |> unique_constraint(:email, message: "Email address is already registered")
  end

end

def create(conn, registration_params) do
  changeset = Registration.changeset(%Registration{}, registration_params)
  case  Repo.insert(changeset) do
    {:ok, _registration} ->
      # Success 
    {:error, error} ->
      conn
      |> put_status(:unprocessable_entity)
      |> render(MyApp.ErrorView, "generic.json", error: error)
  end
end

def render("generic.json", error) do
  error
end

def translate_errors(changeset) do
  Ecto.Changeset.traverse_errors(changeset, &translate_error/1)
end

def render("error.json", %{changeset: changeset}) do
  # When encoded, the changeset returns its errors
  # as a JSON object. So we just pass it forward.
  %{errors: translate_errors(changeset)}
end

def create(conn, registration_params) do
  changeset = Registration.changeset(%Registration{}, registration_params)
  case  Repo.insert(changeset) do
    {:ok, _registration} ->
      # Success 
    {:error, changeset} ->
      conn
      |> put_status(:unprocessable_entity)
      |> render(MyApp.ErrorView, "error.json", changeset: changeset)
  end
end

defmodule MyAppWeb.ErrorHelpers do
  def translate_error({msg, opts}) do
    if count = opts[:count] do
      Gettext.dngettext(MyAppWeb.Gettext, "errors", msg, msg, count, opts)
    else
      Gettext.dgettext(MyAppWeb.Gettext, "errors", msg, opts)
    end
  end
end

---

错误是exto.Changeset的一部分，而不是模型，因此看起来很奇怪。能否提供呈现json的控制器代码和可能的视图代码？@Svilen添加了控制器和视图代码。我尝试了几种将变更集错误传递到json视图的方法，但到目前为止没有任何乐趣。你知道

translate_error/1

函数是在哪里定义的吗？@Jean PierreBécotte我已经用函数定义更新了答案。干得好，@Razzildinho！