How do I convert plug params to optional params?

Questions / Help
,
1

Hello ,

I have created a simple plug in elixir which codes are below :

defmodule TrangellCmsService.Cms.Plugs.AdminChecker do
	import Plug.Conn
	import Phoenix.Controller

	def init(_params) do

	end

	def call(%Plug.Conn{params: %{"acl" => acl}} = conn, params) do

		admin_checker = case acl do
			"admin" ->
				assign(conn, :admin_checker, params)
		  _ ->
				conn
					|> put_status(403)
					|> json(%{error_code: "403", error_msg: "You don't have an access."})
					|> halt()
		end
		admin_checker
	end
end

I have an 500 error when my user didn’t send All params like acl , but I need to show 404 error.

How do I convert plug params to optional params like this function params: defp helper(list, joiner \\ " ") do, then I was trying do it in Plug, but didn’t work , like this def call(%Plug.Conn{params: %{"acl" => acl \\ " "}} = conn, params) do

it should be noted, my user may not send the acl params, for this purpose I need to check this.

thanks.

2

Rough draft using multiheaded function clause:

def call(%Plug.Conn{params: %{"acl" => acl}} = conn, params) do
  case acl do
    "admin" ->
      assign(conn, :admin_checker, params)

    _ ->
      conn
      |> put_status(403)
      |> json(%{error_code: "403", error_msg: "You don't have an access."})
      |> halt()
  end
end

def call(conn, _params) do
  conn
  |> put_status(404)
  |> halt()
end

I also took the freedom to realign your initial code a bit to make it more idiomatic.

Also, I’m not sure if you should import Phoenix.Controller in a Plug. I’m also not a friend of import Plug.Conn and prefer the more more explicit alias Plug.Conn. In generall I am very, very careful with imports at all.

1 Like
3

I still have an 500 error:

[error] #PID<0.457.0> running TrangellCmsServiceWeb.Endpoint terminated
Server: localhost:4022 (http)
Request: PUT /api/edit-category
** (exit) an exception was raised:
    ** (Plug.Conn.NotSentError) a response was neither set nor sent from the connection
        (plug) lib/plug/adapters/cowboy/handler.ex:45: Plug.Adapters.Cowboy.Handler.maybe_send/2
        (plug) lib/plug/adapters/cowboy/handler.ex:17: Plug.Adapters.Cowboy.Handler.upgrade/4
        (cowboy) /Applications/MAMP/htdocs/elixir-ex-source/Trangell_Main/trangell_cms_service_umbrella/deps/cowboy/src/cowboy_protocol.erl:442: :cowboy_protocol.execute/4

my code :

4

when I add Json line , my code works for me

def call(conn, _params) do
	  conn
	  |> put_status(404)
		|> json(%{error_code: "403", error_msg: "You don't have an access."})
	  |> halt()
	end

why does it have a behaviour?

5

Well, you need to put a body into the response, I forgot it in my example, but you can do that by your favored method.

1 Like
6

I used import in my project , because the doc used this.

You helped me a lot. Thank you