Controllers on vanilla plug router

Questions / Help
,
1

Hello everyone, is it possible to dispatch a request to a specific module using plug.router? Phoenix does it using its own macros but I’d like to know how to achieve the same or at least close results using only plug.router

2

Hi @newton-peixoto yes there are examples of this on the first page of the plug docs, give it a whirl and we’ll be here if you run into issues!

3

Hello, thanks for replying. I read the doc but I’m probably missing something. The closest thing that I found was the foward macro but it fowards to another plug not to a module with implementation maybe the :do option should do it?

EDIT#

I was thinking something like this

get "/baz", do: &HelloWorld.Controller.show/1

but it did not work

4

The convention is to do this:

get "/baz", HelloWorld.Controller, :show

the :show atom represents the name of the controller action that will handle the incoming request.

A controller action is a specific type of function that is designed to handle a specific type of request.

Phoenix is basically a giant function on a web connection (and then socket) that is broken down into a tiny steps so controller action functions would always need an arity of at least 2: one parameter for the connection and one for any parameters that might be needed for the change to the connection.

5

Off the top of my head, it might be worth trying to pass in conn without using the capture operator. Also, check out these other requirements from the Plug.Router docs:

Each route receives a conn variable containing a Plug.Conn struct and it needs to return a connection, as per the Plug spec…
Each Plug.Router has a plug pipeline, defined by Plug.Builder, and by default it requires two plugs: :match and :dispatch. ``

So maybe something like this for a minimal example using only Plug.Router:

defmodule AppRouter do
  use Plug.Router

  plug :match # required by default
  plug :dispatch # required by default

  get "/baz" do
    HelloWorld.Controller.show(conn) # must accept and return a connection
  end
end
6

Another option is using forward. Phoenix controllers are also module plugs with MyApp.Controller.call(conn, :action)

So e.g.

defmodule AppRouter do
  use Plug.Router

  plug :match # required by default
  plug :dispatch # required by default

  forward "/baz", to: HelloWorld.Controller, init_opts: :show
end

Keep in mind that Plug.Router.forward has different options than Phoenix.Router.forward, so don’t confuse them.