What's the alternative of before_filter from Rails in Phoenix/Elixir? - rest

Question

In my Phoenix application, I have a pipe and scope "api"
pipeline :api do
plug(:accepts, ["json"])
end
scope "/api" .....
# .....
end
How can I protect it by an API Key which is passed through a special header? That is, I'd like something like this:
defmodule MyApp.MyController do
use MyApp.Web, :controller
:before_filter :authenticate_user_by_api_key!
def authenticate_user_by_api_key!(conn, params) do
# check if a header exists and key is valid
end
end
I'm planning on validating a header. How can I do that without relying on any third-party libraries?
Also. If I wanted to use a module instead of a single function, how would I do that?

Answer 1

Local Plug
If it's a local method, you can simply use the plug construct within the controller.
defmodule MyApp.MyController do
use MyApp.Web, :controller
plug :authenticate_user_by_api_key!
defp authenticate_user_by_api_key!(conn, params) do
# Authenticate or something
end
end
See this answer and read more about Plugs here.
Module Plug
If you'd like to call the function from a Module, your module must export the init/1 and call/2 methods:
defmodule MyApp.Plugs.Authentication do
import Plug.Conn
def init(default), do: default
def call(conn, default) do
# Check header for API Key
end
end
And use it like this in your controller:
defmodule MyApp.MyController do
use MyApp.Web, :controller
plug MyApp.Plugs.Authentication
# Controller Methods
end
Read the Phoenix Guide on Module Plugs for more details.