I’m new to elixir and functional programming, in general. I want to ask what’s the idiomatic way to validate our input parameters? Say I want to do this in my UserController.create.

Check if password is valid by PasswordManager.valid?/1
If not, render error
else, continue

This is what I’ve come up with:

defmodule MyApp.UserController do
  def create(conn, %{"data" => data}) do
    case PasswordManager.valid? user_attrs["password"] do
      {:ok, raw_password} ->
        # make changeset with hashed password
        case Repo.insert(changeset) do
          {:ok, user} ->
            # success
          {:error, invalid_changeset} ->
            # render failure  
      {:error, reason} ->
        render(conn, :errors, data: reason)
    end
  end
end

The issue here is the “ugly” nesting seems unnecessary. I’m looking for a “return early” statements but I guess elixir wants us to write pure functions as much as possible and utilize pattern matching accordingly. How do I refactor this?

Coming from python, I would do this:

def create(user_attrs):
  if not PasswordManager.is_valid(user_attrs['password']):
    # display error
    return
  
  # continue

But what’s the best practice in elixir?

Feel free to do some nitpicks to my code so I can improve writing in this language.

Also, please do note that I’m asking this as a generic question. I hope you don’t dwell too much with the password validation as an example. Thank you.