elixir - (RuntimeError) 预期 action/2 返回一个 Plug.Conn，所有的 Plugs 都必须接收一个连接 (conn) 并返回一个连接

Question

在我的一个 Controller 中，我有以下代码(摘录):

case HTTPoison.get("https://*****.zendesk.com/api/v2/users/search.json?query=" <> clid, headers, [hackney: hackney]) do
  {:ok, %HTTPoison.Response{status_code: 200, body: body}} ->
    conn
    |> put_status(200)
    |> json(body)
  {:ok, %HTTPoison.Response{status_code: 404}} ->
    conn
    |> put_status(404)
    |> json(%{error_code: "404", reason_given: "Resource not found."})
  {:error, %HTTPoison.Error{reason: reason}} ->
    conn
    |> put_status(500)
    |> json(%{error_code: "500", reason_given: "None."})
end

当我运行代码时，它工作正常，但 Phoenix 抛出了运行时异常:

** (exit) an exception was raised:
    ** (RuntimeError) expected action/2 to return a Plug.Conn, all plugs must receive a connection (conn) and return a connection
        (zentonies) web/controllers/page_controller.ex:1: Zentonies.PageController.phoenix_controller_pipeline/2
        (zentonies) lib/zentonies/endpoint.ex:1: Zentonies.Endpoint.instrument/4
        (zentonies) lib/phoenix/router.ex:261: Zentonies.Router.dispatch/2
        (zentonies) web/router.ex:1: Zentonies.Router.do_call/2
        (zentonies) lib/zentonies/endpoint.ex:1: Zentonies.Endpoint.phoenix_pipeline/1
        (zentonies) lib/plug/debugger.ex:93: Zentonies.Endpoint."call (overridable 3)"/2
        (zentonies) lib/zentonies/endpoint.ex:1: Zentonies.Endpoint.call/2
        (plug) lib/plug/adapters/cowboy/handler.ex:15: Plug.Adapters.Cowboy.Handler.upgrade/4
        (cowboy) src/cowboy_protocol.erl:442: :cowboy_protocol.execute/4

我究竟做错了什么？

Answer 1

堆栈跟踪告诉您您的 Controller 操作没有返回 Plug.Conn结构。在 Elixir 中，返回函数的最后一个表达式的结果。查看函数的最后一行并确保它返回 case 表达式的结果。

def(conn, params) do
  final_conn = 
    case HTTPoison.get("https://*****.zendesk.com/api/v2/users/search.json?query=" <> clid, headers, [hackney: hackney]) do
      {:ok, %HTTPoison.Response{status_code: 200, body: body}} ->
        conn
        |> put_status(200)
        |> json(body)
      {:ok, %HTTPoison.Response{status_code: 404}} ->
        conn
        |> put_status(404)
        |> json(%{error_code: "404", reason_given: "Resource not found."})
      {:error, %HTTPoison.Error{reason: reason}} ->
        conn
        |> put_status(500)
        |> json(%{error_code: "500", reason_given: "None."})
    end

  do_something_else(params)

  final_conn
end