Return statement in Elixir

Question

I need a function with some kind of a step-by-step logic and I wonder how I can make one. Let\'s take a log in process on a site as an example, so I need the following logic

Answer 1

This is exactly the situation I'd use elixir pipes library

defmodule Module do
  use Phoenix.Controller
  use Pipe

  plug :action

  def action(conn, params) do
    start_val = {:ok, conn, params}
    pipe_matching {:ok, _, _},
      start_val
        |> email_present
        |> email_length
        |> do_action
  end

  defp do_action({_, conn, params}) do
    # do stuff with all input being valid
  end

  defp email_present({:ok, _conn, %{ "email" => _email }} = input) do
    input
  end
  defp email_present({:ok, conn, params}) do
    bad_request(conn, "email is a required field")
  end

  defp email_length({:ok, _conn, %{ "email" => email }} = input) do
    case String.length(email) > 5 do
      true -> input
      false -> bad_request(conn, "email field is too short")
  end

  defp bad_request(conn, msg) do
    conn 
      |> put_status(:bad_request) 
      |> json( %{ error: msg } )
  end
end

Note, this produces long pipes a lot of times and it is addictive :-)

Pipes library has more ways to keep piping than pattern matching I used above. Have a look elixir-pipes at the examples and tests.

Also, if validation becomes a common theme in your code maybe it is time to check Ecto's changeset validations or Vex another library that does nothing else but validate your input.